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| [[Image:327d.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_327d| PDB=327d | SCENE= }} | | {{STRUCTURE_327d| PDB=327d | SCENE= }} |
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| '''CRYSTAL STRUCTURES OF D(GM5CGM5CGCGCGC)'''
| | ===CRYSTAL STRUCTURES OF D(GM5CGM5CGCGCGC)=== |
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| ==Overview==
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| It is well known that methylation of alternating Py x Pu sequences potentiates the formation of Z-DNA. However, we have now observed that methylation of the alternating Z-DNA oligomer d(GCGCGCGCGC), which starts with a 5'-purine, unexpectedly stabilizes the A-DNA conformation. The double methyl derivative d(Gm5CGm5CGCGCGC), which crystallizes as duplex A-DNA in the hexagonal space group P6(1)22, a = b = 39.33 A and c = 77.93 A with one strand per asymmetric unit and six duplexes in the unit cell, refined to an R factor of 19.1 for 204 DNA atoms and 43 solvent molecules. This is the first report of a DNA sequence crystallized in both right and left-handed conformations, allowing structural comparisons not previously possible and, more importantly, this is the first time that methylation has been shown to potentiate the formation of A-DNA from a sequence known to crystallize as Z-DNA. From this study, ten base-pairs appear to be the critical length in determining the handedness of d(GC)n-type sequences in the crystalline state. Because methylation of nuclear DNA is linked to a number of cellular processes, including transcriptional inactivation, this study has important implications for the role of A-DNA in methylated regions of genomic DNA and, thus, in the regulation of gene expression. In this context, the structure of d(Gm5Cm5CGCGCGC) will be compared with that of the alternating A-DNA decamer d(GCACGCGTGC) and the alternating Z-DNA decamer d(GCGCGCGCGC) and discussed in terms of the forces that govern the handedness of duplex DNA oligomers.
| | The line below this paragraph, {{ABSTRACT_PUBMED_9236126}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 9236126 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_9236126}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Double helix]] | | [[Category: Double helix]] |
| [[Category: Modified]] | | [[Category: Modified]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 20:15:53 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 12:53:35 2008'' |
