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Topics - xiangjun

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1
The DSSR-PyMOL schematics have been featured in all 12 cover images (January to December) of the RNA Journal in 2021. Moreover, the January 2022 issue of RNA continues to highlight DSSR-enabled schematics (see the note below). In the current Covid-19 pandemic, this cover seems to be a fit for the upcoming Christmas holiday season.

Quote
Ebola virus matrix protein octameric ring (PDB id: 7K5L; Landeras-Bueno S, Wasserman H, Oliveira G, VanAernum ZL, Busch F, Salie ZL, Wysocki VH, Andersen K, Saphire EO. 2021. Cellular mRNA triggers structural transformation of Ebola virus matrix protein VP40 to its essential regulatory form. Cell Rep 35: 108986). The Ebola virus matrix protein (VP40) forms distinct structures linked to distinct functions in the virus life cycle. VP40 forms an octameric ring-shaped (D4 symmetry) assembly upon binding of RNA and is associated with transcriptional control. RNA backbone is displayed as a red ribbon; block bases use NDB colors: A—red, G—green, U—cyan; protein is displayed as a gold ribbon. Cover image provided by the Nucleic Acid Database (ndbserver.rutgers.edu). Image generated using DSSR and PyMOL (Lu XJ. 2020. _Nucleic Acids Res_ *48*: e74).

Thanks to Dr. Cathy Lawson at the NDB for generating these cover images using DSSR and PyMOL for the RNA Journal. I'm gratified that the 2020 NAR paper is explicitly acknowledged: it's the first time I've published as a single author in my scientific career.


Did you know that you can easily generate similar DSSR-PyMOL schematics via the http://skmatic.x3dna.org/ website? It is "simple and effective", "good for teaching", and has been highly recommended by Dr. Quentin Vicens (CU Denver) in FacultyOpinions.com.



The 12 PDB structures illustrated in the 2021 covers are:
  • January 2021 "iMango-III fluorescent aptamer (PDB id: 6PQ7; Trachman III RJ, Stagno JR, Conrad C, Jones CP, Fischer P, Meents A, Wang YX, Ferre-D'Amare AR. 2019. Co-crystal structure of the iMango-III fluorescent RNA aptamer using an X-ray free-electron laser. Acta Cryst F 75: 547). Upon binding TO1-biotin, the iMango-III aptamer achieves the largest fluorescence enhancement reported for turn-on aptamers (over 5000-fold)."
  • February 2021 "Human adenosine deaminase (E488Q mutant) acting on dsRNA (PDB id: 6VFF; Thuy-Boun AS, Thomas JM, Grajo HL, Palumbo CM, Park S, Nguyen LT, Fisher AJ, Beal PA. 2020. Asymmetric dimerization of adenosine deaminase acting on RNA facilitates substrate recognition. Nucleic Acids Res. https://doi.org/10.1093/nar/gkaa532). Adenosine deaminase enzymes convert adenosine to inosine in duplex RNA, a modification that strongly affects RNA structure and function in multiple ways."
  • March 2021 "Hepatitis A virus IRES domain V in complex with Fab (PDB id: 6MWN; Koirala D, Shao Y, Koldobskaya Y, Fuller JR, Watkins AM, Shelke SA, Pilipenko EV, Das R, Rice PA, Piccirilli JA. 2019. A conserved RNA structural motif for organizing topology within picornaviral internal ribosome entry sites. Nat Commun 10: 3629)."
  • April 2021 "Mouse endonuclease V in complex with 23mer RNA (PDB id: 6OZO; Wu J, Samara NL, Kuraoka I, Yang W. 2019. Evolution of inosine-specific endonuclease V from bacterial DNase to eukaryotic RNase. Mol Cell 76: 44). Endonuclease V cleaves the second phosphodiester bond 3′ to a deaminated adenosine (inosine). Although highly conserved, EndoV change substrate preference from DNA in bacteria to RNA in eukaryotes."
  • May 2021 "Manganese riboswitch from Xanthmonas oryzae (PDB id: 6N2V; Suddala KC, Price IR, Dandpat SS, Janeček M, Kührová P, Šponer J, Banáš P, Ke A, Walter NG. 2019. Local-to-global signal transduction at the core of a Mn2+ sensing riboswitch. Nat Commun 10: 4304). Bacterial manganese riboswitches control the expression of Mn2+ homeostasis genes. Using FRET, it was shown that an extended 4-way-junction samples transient docked states in the presence of Mg2+ but can only dock stably upon addition of submillimolar Mn2+."
  • June 2021 "Sulfolobus islandicus Csx1 RNase in complex with cyclic RNA activator (PDB id: 6R9R; Molina R, Stella S, Feng M, Sofos N, Jauniskis V, Pozdnyakova I, Lopez-Mendez B, She Q, Montoya G. 2019. Structure of Csx1-cOA4 complex reveals the basis of RNA decay in Type III-B CRISPR-Cas. Nat Commun 10: 4302). CRISPR-Cas multisubunit complexes cleave ssRNA and ssDNA, promoting the generation of cyclic oligoadenylate (cOA), which activates associated CRISPR-Cas RNases. The Csx1 RNase dimer is shown with cyclic (A4) RNA bound."
  • July 2021 "M. tuberculosis ileS T-box riboswitch in complex with tRNA (PDB id: 6UFG; Battaglia RA, Grigg JC, Ke A. 2019. Structural basis for tRNA decoding and aminoacylation sensing by T-box riboregulators. Nat Struct Mol Biol 26: 1106). T-box riboregulators are a class of cis-regulatory RNAs that govern the bacterial response to amino acid starvation by binding, decoding, and reading the aminoacylation status of specific transfer RNAs."
  • August 2021 "CAG repeats recognized by cyclic mismatch binding ligand (PDB id: 6QIV; Mukherjee S, Blaszczyk L, Rypniewski W, Falschlunger C, Micura R, Murata A, Dohno C, Nakatan K, Kiliszek A. 2019. Structural insights into synthetic ligands targeting A–A pairs in disease-related CAG RNA repeats. Nucleic Acids Res 47:10906). A large number of hereditary neurodegenerative human diseases are associated with abnormal expansion of repeated sequences. RNA containing CAG repeats can be recognized by synthetic cyclic mismatch-binding ligands such as the structure shown."
  • September 2021 "Corn aptamer complex with fluorophore Thioflavin T (PDB id: 6E81; Sjekloca L, Ferre-D'Amare AR. 2019. Binding between G quadruplexes at the homodimer interface of the Corn RNA aptamer strongly activates Thioflavin T fluorescence. Cell Chem Biol 26: 1159). The fluorescent compound Thioflavin T, widely used for the detection of amyloids, is bound at the dimer interface of the homodimeric G-quadruplex-containing RNA Corn aptamer."
  • October 2021 "Cas9 nuclease-sgRNA complex with anti-CRISPR protein inhibitor (PDB id: 6JE9; Sun W, Yang J, Cheng Z, Amrani N, Liu C, Wang K, Ibraheim R, Edraki A, Huang X, Wang M, et al. 2019. Structures of Neisseria meningitidis Cas9 complexes in catalytically poised and anti-CRISPR-inhibited states. Mol Cell 76: 938­–952.e5). Nme1Cas9, a compact nuclease for in vivo genome editing. AcrIIC3 is an anti-CRISPR protein inhibitor."
  • November 2021 "Two-quartet RNA parallel G-quadruplex complexed with porphyrin (PDB id: 6JJI; Zhang Y, Omari KE, Duman R, Liu S, Haider S, Wagner A, Parkinson GN, Wei D. 2020. Native de novo structural determinations of non-canonical nucleic acid motifs by X-ray crystallography at long wavelengths. Nucleic Acids Res 48: 9886–9898)."
  • December 2021 "Structure of S. pombe Lsm1–7 with RNA, polyuridine with 3' guanosine (PDB id: 6PPV; Montemayor EJ, Virta JM, Hayes SM, Nomura Y, Brow DA, Butcher SE. 2020. Molecular basis for the distinct cellular functions of the Lsm1–7 and Lsm2–8 complexes. RNA 26: 1400–1413). Eukaryotes possess eight highly conserved Lsm (like Sm) proteins that assemble into circular, heteroheptameric complexes, bind RNA, and direct a diverse range of biological processes. Among the many essential functions of Lsm proteins, the cytoplasmic Lsm1–7 complex initiates mRNA decay, while the nuclear Lsm2–8 complex acts as a chaperone for U6 spliceosomal RNA."

2
Site announcements / BioExcel webinar on DSSR
« on: November 23, 2021, 11:38:53 am »
On December 9, 2021, at 15:00 CET, I will present a BioExcel webinar titled "X3DNA-DSSR, a resource for structural bioinformatics of nucleic acids."

For the record, the screenshot of the announcement is shown below:


3
Site announcements / No more grant funding for 3DNA/DSSR
« on: October 30, 2021, 09:58:15 pm »
Due to a lack of governmental funding support, we are no longer able to provide DSSR free of charge to the community. Instead, we offer DSSR Pro for academic purposes for a one-time fee of $1000, which includes one year of developer support as set forth in the license agreement, and can be requested from techtransfer@columbia.edu, copy xiangjun@x3dna.org. Commercial users may inquire about pricing and licensing terms by emailing techtransfer@columbia.edu, copy xiangjun@x3dna.org. DSSR Pro excels in structural bioinformatics of RNA, DNA, and their protein complexes. The software has completely superseded 3DNA, and is being continuously improved. Revenue from licensing supports the development and availability of DSSR.

My focus is now on DSSR Pro, and I am committed to making it a brand that stands for quality and value. By virtue of its unmatched functionality, usability, and support, DSSR Pro would save users a substantial amount of time and effort when compared to competing options.

I designed, implemented, documented, and have continuously improved and supported DSSR. As a result, DSSR Pro users may expect a rapid and concrete answer to their questions. My track record throughout the years has unambiguously demonstrated my dedication to DSSR. I strive to ensure that paying users' trust in DSSR Pro is well-founded by providing them with the best services possible.

As a general rule, the CTV does not provide an evaluation license of DSSR Pro. Potential users should watch the DSSR overview video (20m), browse the Forum, and read DSSR-related papers. If they still have questions or want to see a live demo, I would be pleased to accommodate them. Although more DSSR Pro licenses are definitely beneficial, I do not have the time or desire to directly promote the product, including sending bulk emails to Forum registered users. As the developer, I can only strive to make DSSR Pro the best it can be and let the rest sort itself out. I am a strong believer of the old Chinese saying: "酒香不怕巷子深" (Good wine needs no bush).


3DNA and DSSR Basic are obsolete and will no longer be maintained or supported. Thanks to the revenue from DSSR Pro licenses, however, the following web-based resources remain accessible to the general public:
Additionally, the 3DNA Forum will be maintained so that people can assist one another and archived content would remain accessible. I may chime in occasionally, but I will not be able to continue serving the community for free as I did over the past decade.


4
Site announcements / Clarification on DSSR licensing
« on: May 31, 2021, 01:58:55 pm »
Once in a while I receive emails from prospective users, both commercial and academic, about DSSR licensing from the Columbia Technology Venture (CTV). Louis made the following explicit suggestion in a recent thread titled "Bug or feature (?) : residue numbering not understood":

Quote from: Louis
I suggest you summarize the content of the [CTV] page in a forum post, to provide a reliable source of information about DSSR licensing, maybe?

There are two types of DSSR Pro licenses, as shown below:
  • Commercial users may inquire about pricing and licensing terms by emailing techtransfer@columbia.edu (and CC to xiangjun@x3dna.org).

  • Academic users can obtain DSSR Pro for a one-time fee of $1000, which includes a comprehensive user manual and one year of developer support as set forth in the license agreement. Please contact techtransfer@columbia.edu (and CC to xiangjun@x3dna.org). DSSR Pro has completely superseded 3DNA, and is being continuously improved.
Users of DSSR Pro, both commercial and academic, receive first-rate support directly from the developer. The open 3DNA Forum, private email, and virtual meetings are all options for contact, depending on what is most convenient for the users.

The free DSSR Basic academic license is no longer available as of November 11, 2021. Due to a lack of government funding, only DSSR Pro is offered for academic and commercial usage as outlined above. For further information, please visit the CTV DSSR website.

Xiang-Jun

7
Site announcements / Video: an overview of DSSR
« on: May 01, 2021, 01:32:37 pm »
I've just released a video "An overview of DSSR" -- http://docs.x3dna.org/dssr-overview/.

DSSR already has a large user base. Based on my observation, however, DSSR is still heavily underused for what it has to offer. This DSSR overview video is for new DSSR users, as well as existing ones.

As always, I appreciate your feedback.

Best regards,

Xiang-Jun

8
FAQs / MOVED: X3DNA and cif
« on: April 30, 2021, 10:45:41 am »

11
General discussions (Q&As) / MOVED: Circular DNA parameters
« on: February 18, 2021, 11:07:07 am »

12
Recently, while visiting the NAR website on DSSR-enabled innovative schematics of 3D nucleic acid structures with PyMOL, I noticed a big red circle near “View Metrics”. The symbol is very obvious and a bit 'alarming'. I was curious to see what it meant. After a few clicks, I was delighted to read the following recommendation in Faculty Opinions by Quentin Vicens:

Quote
I really enjoyed “playing” with the revised and expanded version of Dissecting the Spatial Structure of RNA (DSSR) described by Xiang-Jun Lu in this July issue of NAR. The software is known to generate ‘block view’ representations of nucleic acids that make many parameters more immediately visible, such as base composition, stacking, and groove depth. This new version includes Watson-Crick pairs shown as single rectangles, and G quadruplexes as large squares, making such regions more quickly distinguishable from other regions within an overall tertiary structure. I was amazed at how simple and effective the web interface was, and I liked the possibility to download a PyMOL session to look at molecules under different angles. If need be, blocks can be further edited in PyMOL using the provided plugin (see on page 35). I highly recommend it!

The DSSR-PyMOL schematics paper/website has been rated “Very Good”, and classified as “Good for Teaching”. See Vicens Q: Faculty Opinions Recommendation of [Lu XJ, Nucleic Acids Res 2020 48(13):e74]. In Faculty Opinions, 14 Aug 2020; 10.3410/f.738001682.793577327. A screenshot is attached below.


13
Site announcements / DSSR 2.0 is licensed by Columbia University
« on: August 24, 2020, 08:35:04 am »
DSSR 2.0 is out. It integrates an unprecedented set of features into one computational tool, including analysis/annotation, schematic visualization, and model building of 3D nucleic acid structures. DSSR 2.0 supersedes 3DNA 2.4, which is still maintained but no additional features other than bug fixes are scheduled. See the DSSR 2.0 overview PDF.

DSSR delivers a great user experience by solving problems and saving time. Considering its usability, interoperability, features, and support, DSSR easily stands out among 'competitors'. It exemplifies a 'solid software product'. I strive to make DSSR a pragmatic tool that the structural bioinformatics community can count on.

DSSR 2.0 is licensed by Columbia University. The software remains free for academic users, with the basic user manual. The professional user manual (over 230 pages, including 7 appendices) is available for paid academic users or commercial users only. Licensing revenue helps ensure the long-term sustainability of the DSSR project.

Additionally, the paper "DSSR-enabled innovative schematics of 3D nucleic acid structures with PyMOL" has recently been published in Nucleic Acids Research, 48(13):e74. Check the web interface.

The DSSR-PyMOL paper/website has been rated "very good" and classified as "Good for Teaching". See Vicens Q: Faculty Opinions Recommendation of [Lu XJ, Nucleic Acids Res 2020 48(13):e74]. In Faculty Opinions, 14 Aug 2020; 10.3410/f.738001682.793577327.

14
General discussions (Q&As) / MOVED: RNA Journal Covers
« on: July 28, 2020, 03:38:07 pm »

16
Bug reports / MOVED: modified nucleotides incorrect.
« on: February 05, 2020, 08:54:25 am »

18
This website http://skmatic.x3dna.org/ (see screenshot below) aims to showcase DSSR-enabled cartoon-block schematics of nucleic acid structures using PyMOL. It presents a simple interface to browse pre-calculated PDB entries with a set of default settings: long rectangular blocks for Watson-Crick base-pairs, square blocks for G-tetrads in G-quadruplexes, with minor-groove edges in black. Users can also specify an URL to a PDB- or mmCIF-formatted file or upload such an atomic coordinates file directly, and set several common options to customerize to the rendered image.

Moreover, a web API to DSSR-PyMOL schematics is available to allow for its easy integration into third-party tools.


Input a PDB id
Pre-calculated cartoon-block images together with summary information are available for PDB entries of nucleic-acid-containing structures. Note that gigantic structures like ribosomes that are only represented in mmCIF format are excluded from the resource. The base block images are most effective for small to medium-sized structures.

Here are a few examples:
  • 1ehz, the crystal structure of yeast phenylalanine trna at 1.93-A resolution
  • 2lx1, the major conformation of the internal loop 5'GAGU/3'UGAG
  • 2grb, the crystal structure of an RNA quadruplex containing inosine-tetrad
  • 4da3, the crystal structure of an intramolecular human telomeric DNA G-quadruplex 21-mer bound by the naphthalene diimide compound MM41
  • 1oct, crystal structure of the Oct-1 POU domain bound to an octamer site
  • 2hoj, the crystal structure of an E. coli thi-box riboswitch bound to thiamine pyrophosphate, manganese ions

Each entry is shown with images in six orthogonal perspectives: front, back, right, left, top, bottom. The 'front' image (upper-left in the panel) is oriented into the most-extended view with the DSSR --blocview option. The corresponding PyMOL session file and PDB coordinate file are available for download. One can also visualize the structure interactively via 3Dmol.js.

Sample PDB entries
Users can browse random samples of pre-calculated PDB entries. The number should be between 3 and 99, with a default of 12 entries (see below for an example). Simply click the 'Submit' button or the link "Random samples (3 to 99)" to see random results of 12 entries each time.

Specify an coordinate file
The atomic coordinate file must be in PDB or mmCIF format, and can be optionally gzipped (.gz). One can either specify an URL to or select a coordinate file. Several common options are available to allow for user customizations.

Web API help message
Usage with 'http' (HTTPie):
    http -f http://skmatic.x3dna.org/api [options] url=|model@
    http http://skmatic.x3dna.org/api/pdb/pdb_id  -- for a pre-calculated PDB entry
    http http://skmatic.x3dna.org/api/help        -- display this help message
Options:
    block_file=styles-in-free-text-format [e.g., block_file=wc-minor]
    block_color=nt-selection-and-color    [e.g., block_color='A:pink']
    block_depth=thickness-of-base-block   [e.g., block_depth=1.2]
    r3d_file=true-or-FALSE(default)       [e.g., r3d_file=true]
    raw_xyz=true-or-FALSE(default)        [e.g., raw_xyz=true]
Required parameter
    url=URL-to-coordinate-file [e.g., url=https://files.rcsb.org/download/1ehz.pdb.gz]
    model@coordinate-file      [e.g., model@1ehz.cif]
    # Only one must be specified. 'url' precedes 'model' when both are specified.
    # The coordinate file must be in PDB or PDBx/mmCIF format, optionally gzipped.
Examples
    http -f http://skmatic.x3dna.org/api block_file='wc-minor' model@1ehz.cif r3d_file=t
    http -f http://skmatic.x3dna.org/api url=https://files.rcsb.org/download/1ehz.pdb.gz -d -o 1ehz.png
    http http://skmatic.x3dna.org/api/pdb/1ehz -d -o 1ehz.png
    # with 'curl'
    curl http://skmatic.x3dna.org/api -F 'model=@1msy.pdb' -F 'block_file=wc-minor' -F 'r3d_file=1'
    curl http://skmatic.x3dna.org/api -F 'url=https://files.rcsb.org/download/1ehz.pdb.gz' -o 1ehz.png
    curl http://skmatic.x3dna.org/api/pdb/1ehz -o 1ehz.png

Sample images
       

19
Feature requests / MOVED: building circular DNA
« on: July 16, 2019, 11:56:46 am »

20
It is a great pleasure to see that our article "Web 3DNA 2.0 for the analysis, visualization, and modeling of 3D nucleic acid structures" has been highlighted in the cover page of the web server issue of NAR’19. According to the editor, This year, 331 proposals were submitted and 122, or 37%, were approved for manuscript submission. Of those approved, 94, or 77%, were ultimately accepted for publication. Overall, that corresponds to a ~28% acceptance rate.

The cover image and its caption are shown below. Moreover, details on how the cover image was created are available on the 3DNA Forum.

Caption: Examples of customized molecular models that can be generated with 3DNA: (top) a chromatin-like, nucleosome-decorated DNA with the structures of known histone-DNA assemblies placed at user-defined binding sites; (lower left) molecular schematic of a DNA trinucleotide diphosphate illustrating the base planes and reference frames used to construct and analyze 3D nucleic acid-containing structures; (lower right) customized single-stranded tRNA model built from a user-defined base sequence and a set of rigid-body parameters describing the desired placement of successive bases. Color code of base blocks: A, red; C, yellow; G, green; T, blue; U, cyan.

21
"Cover image featuring the web 3DNA 2.0 paper" title="Cover image featuring the web 3DNA 2.0 paper"

Caption: Examples of customized molecular models that can be generated with 3DNA: (top) a chromatin-like, nucleosome-decorated DNA with the structures of known histone-DNA assemblies placed at user-defined binding sites; (lower left) molecular schematic of a DNA trinucleotide diphosphate illustrating the base planes and reference frames used to construct and analyze 3D nucleic acid-containing structures; (lower right) customized single-stranded tRNA model built from a user-defined base sequence and a set of rigid-body parameters describing the desired placement of successive bases. Color code of base blocks: A, red; C, yellow; G, green; T, blue; U, cyan.



The top image is as Fig. 1E, and the lower-left image is as Fig. 2A. The lower-right image is sort of like Fig. 1D. However, it was actually generated using DSSR and PyMOL with (long) base-pair blocks for Watson-Crick pairs, with he commands used listed below:

Code: Bash
  1. x3dna-dssr -i=1fir-rebuild.pdb --blocview --block-opts=wc-minor -o=1fir-raw.pml
  2.  
  3. # Manually re-oriented the block image: "turn z, -155", and
  4. #     changed the chain color from "red" (default for chain A) to "marine"
  5. #     ray-traced and rendered to a PNG image, "1fir-dssr-pymol.png".
  6. # The revised PYMOL .pml file is named "1fir-dssr.pml"
  7. pymol -qkc 1fir-dssr.pml
  8. # The above PyMOL command generates "1fir-dssr-pymol.png", which is trimmed as below
  9. convert -trim +repage -transparent white 1fir-dssr-pymol.png 1fir-dssr.png

The following key related files are attached:
  • 1fir-rebuild.pdb -- a tRNA model generated with web 3DNA 2.0
  • 1fir-raw.pml -- the PyMOL script crated with DSSR (line #1 above)
  • 1fir-dssr.pml -- manually edited PyMOL script based on 1fir-raw.pml
  • 1fir-dssr.png -- the schematic block images used in the cover image

22
Our research article, "Effects of Noncanonical Base Pairing on RNA Folding: Structural Context and Spatial Arrangements of G·A Pairs", has recently been published in the ACS Biochemistry journal [2019, 58(20), pp.2474-2487]. It covers many aspects of RNA structural analysis and showcases some of the fundamental and unique features available from DSSR. This section is dedicated to topics directly related to the paper, including details for recreating the figures and tables reported therein. For general questions on DSSR, please use the section "RNA structures (DSSR)".

Quote
Noncanonical base pairs play important roles in assembling the three-dimensional structures critical to the diverse functions of RNA. These associations contribute to the looped segments that intersperse the canonical double-helical elements within folded, globular RNA molecules. They stitch together various structural elements, serve as recognition elements for other molecules, and act as sites of intrinsic stiffness or deformability. This work takes advantage of new software (DSSR) designed to streamline the analysis and annotation of RNA three-dimensional structures. The multiscale structural information gathered for individual molecules, combined with the growing number of unique, well-resolved RNA structures, makes it possible to examine the collective features deeply and to uncover previously unrecognized patterns of chain organization. Here we focus on a subset of noncanonical base pairs involving guanine and adenine and the links between their modes of association, secondary structural context, and contributions to tertiary folding. The rigorous descriptions of base-pair geometry that we employ facilitate characterization of recurrent geometric motifs and the structural settings in which these arrangements occur. Moreover, the numerical parameters hint at the natural motions of the interacting bases and the pathways likely to connect different spatial forms. We draw attention to higher-order multiplexes involving two or more G·A pairs and the roles these associations appear to play in bridging different secondary structural units. The collective data reveal pairing propensities in base organization, secondary structural context, and deformability and serve as a starting point for further multiscale investigations and/or simulations of RNA folding.



23
FAQs / Which one is the 3DNA homepage: x3dna.org or home.x3dna.org?
« on: June 07, 2019, 12:11:20 pm »
Content-wise, home.x3dna.org is a duplicate of x3dna.org, so both are the homepage of the 3DNA suite of programs, including DSSR and SNAP.

I registered the x3dna.org domain name and has hosted it on a popular shared web hosting service. Later on, I noticed that the 3DNA website is not acceptable from China, presumably due to the politically sensitive contents of other websites. To cater for the increasingly large number of 3DNA users from China, I created the home.x3dna.org sub-domain which is hosted at Columbia University. As a side note, the 3DNA Forum (forum.x3dna.org) is similarly hosted at Columbia, so it is generally accessible.

24
Site announcements / Web 3DNA 2.0 and G.A pairs in RNA folding
« on: June 07, 2019, 11:48:16 am »
Two papers closely related to 3DNA/DSSR have recently been published, as shown below:
  • "Web 3DNA 2.0 for the analysis, visualization, and modeling of 3D nucleic acid structures" in Nucleic Acids Research (NAR). Here is the abstract, including a graphical illustration.
    Quote
    Web 3DNA (w3DNA) 2.0 is a significantly enhanced version of the widely used w3DNA server for the analysis, visualization, and modeling of 3D nucleic-acid-containing structures. Since its initial release in 2009, the w3DNA server has continuously served the community by making commonly-used features of the 3DNA suite of command-line programs readily accessible. However, due to the lack of updates, w3DNA has clearly shown its age in terms of modern web technologies and it has long lagged behind further developments of 3DNA per se. The w3DNA 2.0 server presented here overcomes all known shortcomings of w3DNA while maintaining its battle-tested characteristics. Technically, w3DNA 2.0 implements a simple and intuitive interface (with sensible defaults) for increased usability, and it complies with HTML5 web standards for broad accessibility. Featurewise, w3DNA 2.0 employs the most recent version of 3DNA, enhanced with many new functionalities, including: the automatic handling of modified nucleotides; a set of ‘simple’ base-pair and step parameters for qualitative characterization of non-Watson–Crick double- helical structures; new structural parameters that integrate the rigid base plane and the backbone phosphate group, the two nucleic acid components most reliably determined with X-ray crystallography; in silico base mutations that preserve the backbone geometry; and a notably improved module for building models of single-stranded RNA, double- helical DNA, Pauling triplex, G-quadruplex, or DNA structures ‘decorated’ with proteins. The w3DNA 2.0 server is freely available, without registration, at http://web.x3dna.org.



    Notably, details for reproducing our reported results (figures and tables) are available in a dedicated section "web 3DNA 2.0 (http://web.x3dna.org)" on the 3DNA Forum.


  • "Effects of Noncanonical Base Pairing on RNA Folding: Structural Context and Spatial Arrangements of G·A Pairs" in ACS Biochemistry. Here is the abstract with a graphical illustration.
    Quote
    Noncanonical base pairs play important roles in assembling the three-dimensional structures critical to the diverse functions of RNA. These associations contribute to the looped segments that intersperse the canonical double-helical elements within folded, globular RNA molecules. They stitch together various structural elements, serve as recognition elements for other molecules, and act as sites of intrinsic stiffness or deformability. This work takes advantage of new software (DSSR) designed to streamline the analysis and annotation of RNA three-dimensional structures. The multiscale structural information gathered for individual molecules, combined with the growing number of unique, well-resolved RNA structures, makes it possible to examine the collective features deeply and to uncover previously unrecognized patterns of chain organization. Here we focus on a subset of noncanonical base pairs involving guanine and adenine and the links between their modes of association, secondary structural context, and contributions to tertiary folding. The rigorous descriptions of base-pair geometry that we employ facilitate characterization of recurrent geometric motifs and the structural settings in which these arrangements occur. Moreover, the numerical parameters hint at the natural motions of the interacting bases and the pathways likely to connect different spatial forms. We draw attention to higher-order multiplexes involving two or more G·A pairs and the roles these associations appear to play in bridging different secondary structural units. The collective data reveal pairing propensities in base organization, secondary structural context, and deformability and serve as a starting point for further multiscale investigations and/or simulations of RNA folding.



    The paper includes a paragraph in the discussion section on differences between 3DNA/DSSR and the well-established LW (Leontis-Westhof) scheme:

    Quote
    Qualitative descriptions of noncanonical RNA base pairing, pioneered by Leontis and Westhof9,41 and linked in this work to the rigid-body parameters of interacting bases, have proven valuable in deciphering the connections between RNA primary, secondary, and tertiary structures. The present categorization is based on the positions of the hydrogen-bonded atoms with respect to a standard, embedded base reference frame30 defined in terms of an idealized Watson−Crick base pair. The major- and minor-groove base edges used here correspond in most cases to what are termed the Hoogsteen and sugar edges in the Leontis−Westhof scheme (one can compare the two classification schemes in Table S2). The + and − symbols introduced in 3DNA24 and DSSR27 unambiguously distinguish the relative orientations of the two bases. The trans and cis designations used in the earlier literature, however, are qualitative in nature and often uncertain. There are many “nc” (near cis, as in ncWW) and “nt” (near trans, as in ntSH) annotations listed in the RNA Structure Atlas; see, for example, the base-pair interactions in the sarcin−ricin domain of E. coli 23S rRNA found by entering PDB entry 1msy at http://rna.bgsu.edu/rna3dhub/pdb. The assignment of qualitative descriptors of RNA associations on the basis of atomic identity alone is generally not clear-cut. Numerical differences in the rigid-body parameters are critical to differentiating pairing schemes that share a common hydrogen bond, e.g., the G(N3)···A(N6) interaction found in m−WII and m−MI arrangements of G and A (Table 1 and Figures 4 and S3). The numerical data also provide a basis for following conformational transitions and may potentially be of value in making functional and other meaningful distinctions among RNA base pairs.

    See also a recent thread Noncanonical base pair standards on the 3DNA Forum and the section titled “3.2.2 Base pairs” in the DSSR User Manual.

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Figure 3. Commonly-used fiber models and in silico base mutations. (A) Six commonly used models highlighted in the ‘Fiber’ module: single-stranded RNA, double-helical A-, B-, and C-form DNA, the Pauling triplex model (32), and the parallel polyI:polyI:polyI:polyI quadruplex. (B) Single-stranded RNA fiber model of base sequence AUCGAUCGAUCG. (C) Double-helical B-DNA fiber model with sequence ATCGATCGATCG on the leading strand. (D) Pauling triplex model with each strand of sequence AAAACCCCGGGG. (E) parallel polyI:polyI:polyI:polyI quadruplex model with 12 layers of hydrogen-bonded hypoxanthine tetrads. Models in (B-E) were generated using the default settings on the w3DNA 2.0 server, each taking just two mouse clicks. (F) All hypoxanthine bases along the poly I chains mutated to guanine via the ‘Mutation’ module, leading to a parallel G-quadruplex. Color code for base blocks: A, red; C, yellow; G, green; T, blue; U, cyan; I, dark green.

Reproducing the results reported in the figure is straightforward via the w3DNA 2.0 interface, by simply clicking a few buttons in each case. Please read tutorials on the 'Fiber' module and the 'Mutation' module online or in the corresponding sections of the supplemental PDF. See also the blogpost "Pauling's triplex model of nucleic acids is available in 3DNA" for details and background information about this model of historical significance. Note the schematic representation allows direct readout of base identity.

Fig. 3A is a screenshot of the header of the 'Fiber' module. The list includes the six commonly used fiber models: single-stranded RNA, double-helical A-, B-, and C-form DNA, the Pauling triplex model, and the parallel polyI:polyI:polyI:polyI quadruplex.

Fig. 3B-D are easily created by clicking two buttons each via the w3DNA 2.0 interface. Please read tutorial on the 'Fiber' module online or the section "S4.5 Modeling module: 56 fiber models" in the supplemental PDF.

Listed below are the 3DNA command-line scripts.
Code: Bash
  1.     # Fig. 3B, single-stranded RNA
  2. fiber -seq=AUCGAUCGAUCG -rna -single fiber-ssRNA.pdb
  3. blocview -x 180 -i fiber-ssRNA.png fiber-ssRNA.pdb
  4.     # Fig. 3C, double-stranded DNA
  5. fiber -seq=ATCGATCGATCG fiber-B-dsDNA.pdb
  6. blocview -i fiber-B-dsDNA.png fiber-B-dsDNA.pdb
  7.     # Fig. 3D, Pauling triplex
  8. fiber --pauling -seq=AAAACCCCGGGG Pauling-triplex.pdb
  9. blocview -x 180 -i Pauling-triplex.png Pauling-triplex.pdb


Fig. 3E is generated by selecting "poly(I) : poly(I) : poly(I) : poly(I)" ("use this model" button) and then clicking "Build" with default repeat number of 12. In the w3DNA 2.0 output, the image is rotated 90 degrees to be in a horizontal orientation.

Fig. 3F is produced by clicking the link "[Use this structure for mutation]", directly after Fig. 3E, to the "Mutation" module. At the top, select the "Mutate to All: G" radio button, and then "Continue".

For Fig. 3E and 3F, please read tutorial on the 'Mutation' module online or the section "S4.6 Modeling module: base mutations" (especially "Example 6-3: Construction of a G-quadruplex DNA model") in the supplemental PDF.

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Created and maintained by Dr. Xiang-Jun Lu [律祥俊] (xiangjun@x3dna.org)
The Bussemaker Laboratory at the Department of Biological Sciences, Columbia University.