Is the DPT tautomerization of the long A·G Watson-Crick DNA base mispair a source of the adenine and guanine mutagenic tautomers? A QM and QTAIM response to the biologically important question.
Journal of computational chemistry.J Comput Chem.2014 Mar 5;35(6):451-66. doi: 10.1002/jcc.23515. Epub 2013 Dec 30.
Herein, we first address the question posed in the title by establishing the tautomerization trajectory via the double proton transfer of the adenine·guanine (A·G) DNA base mispair formed by the canonical tautomers of the A and G bases into the A*·G* DNA base mispair, involving mutagenic tautomer
Mispair-specific recruitment of Mlh1-Pms1 identifies repair substrates of Saccharomyces cerevisiae Msh2-Msh3.
Srivatsan A1, Bowen N, Kolodner RD.Author information 1Ludwig Institute for Cancer Research, United States.AbstractDNA mismatch repair (MMR)a is initiated by either the Msh2-Msh6 or the Msh2-Msh3 mispair recognition heterodimer. Here, we optimized the expression and purification of Saccharomyces cerevisiae Msh2-Msh3 and performed a comparative study of Msh2-Msh3 and Msh2-Msh6 for mispair binding, sliding clamp formation and Mlh1-Pms1 recruitment. Msh2-Msh3 formed sliding clamps and recruited Mlh1-Pms1 on +1, +2, +3 and +4 insertion/deletions and CC, AA and possibly GG mispairs whereas Msh2-Msh6 formed mispair-dependent sliding clamps and recruited Mlh1-Pms1 on 7 of the 8 possible base:base mispairs, the +1 insertion/deletion mispair and to a low level on the +2 but not the +3 or +4 insertion/deletion mispairs and not on the CC mispair. The mispair specificity of sliding clamp formation and Mlh1-Pms1 recruitment but not mispair binding alone correlated best with genetic data on the mispair specificity of Msh2-Msh3- and Msh2-Msh6-dependent MMR in vivo. Analysis of an Msh2-Msh6/Msh3 chimeric protein and mutant Msh2-Msh3 complexes showed that the nucleotide binding domain and communicating regions but not the mispair binding domain of Msh2-Msh3 are responsible for the extremely rapid dissociation of Msh2-Msh3 sliding clamps from DNA relative to that seen for Msh2-Msh6 and that amino acid residues predicted to stabilize Msh2-Msh3 interactions with bent, strand separated mispair-containing DNA are more critical for the recognition of small +1 insertion/deletions than larger +4 insertion/deletions.
The Journal of biological chemistry.J Biol Chem.2014 Feb 18. [Epub ahead of print]
DNA mismatch repair (MMR)a is initiated by either the Msh2-Msh6 or the Msh2-Msh3 mispair recognition heterodimer. Here, we optimized the expression and purification of Saccharomyces cerevisiae Msh2-Msh3 and performed a comparative study of Msh2-Msh3 and Msh2-Msh6 for mispair binding, sliding clamp f
Fidelity of nick sealing by Deinococcus radiodurans RNA ligase: effects of 3' -OH and 5' -PO4 base mispairs and damaged base lesions.
Schmier BJ1, Shuman S.Author information 1Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10065.AbstractDeinococcus radiodurans RNA ligase (DraRnl) is the founding member of a family of end-joining enzymes encoded by diverse microbes and viruses. DraRnl ligates 3' -OH, 5' -PO4 nicks in double-stranded nucleic acids in which the nick 3' -OH end is RNA. Here we gauge effects of 3' -OH and 5' -PO4 base mispairs and damaged base lesions on the rate of nick sealing. DraRnl is indifferent to identity of the 3' -OH nucleobase, provided it is correctly paired. With 3' -OH mispairs, DraRnl sealing rate varies widely, with G:T and A:C mispairs being the best substrates and G:G, G:A and A:A mispairs being the worst. DraRnl accepts 3' A:oxoG as correctly paired, while discriminating against U:oxoG and G:oxoG mispairs. DraRnl displays high activity and low fidelity in sealing 3' -OH ends opposite an oxoA lesion. It prefers 3' -OH adenosine when sealing opposite an abasic template site. With 5' -PO4 mispairs, DraRnl seals a 5' T:G mispair as well as it does a 5' C:G pair; in most other respects, ligation fidelity at 5' mispairs is similar to 3' mispairs. DraRnl accepts a 5' A:oxoG end as correctly paired, yet is more tolerant of 5' T:oxoG and 5' G:oxoG mispairs than the equivalent configurations on the 3' side of the nick. At 5' N:abasic nicks, DraRnl prefers to ligate when the N base is a purine. The biochemical properties of DraRnl are compatible with its participation in the templated repair of RNA damage or in the sealing of filled DNA gaps that have a 3' "ribo-patch".
Journal of bacteriology.J Bacteriol.2014 Feb 14. [Epub ahead of print]
Deinococcus radiodurans RNA ligase (DraRnl) is the founding member of a family of end-joining enzymes encoded by diverse microbes and viruses. DraRnl ligates 3' -OH, 5' -PO4 nicks in double-stranded nucleic acids in which the nick 3' -OH end is RNA. Here we gauge effects of 3' -OH and 5' -PO4 base m
Escherichia coli MutY protein has a guanine-DNA glycosylase that acts on 7,8-dihydro-8-oxoguanine : guanine mispair to prevent spontaneous GC-CG transversions