期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2017
卷号：114
期号：14
页码：3607-3612
DOI：10.1073/pnas.1701753114
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Mammalian and Saccharomyces cerevisiae mismatch repair (MMR) proteins catalyze two MMR reactions in vitro. In one, mispair binding by either the MutS homolog 2 (Msh2)–MutS homolog 6 (Msh6) or the Msh2–MutS homolog 3 (Msh3) stimulates 5′ to 3′ excision by exonuclease 1 (Exo1) from a single-strand break 5′ to the mispair, excising the mispair. In the other, Msh2–Msh6 or Msh2–Msh3 activate the MutL homolog 1 (Mlh1)–postmeiotic segregation 1 (Pms1) endonuclease in the presence of a mispair and a nick 3′ to the mispair, to make nicks 5′ to the mispair, allowing Exo1 to excise the mispair. DNA polymerase δ (Pol δ) is thought to catalyze DNA synthesis to fill in the gaps resulting from mispair excision. However, colocalization of the S. cerevisiae mispair recognition proteins with the replicative DNA polymerases during DNA replication has suggested that DNA polymerase ε (Pol ε) may also play a role in MMR. Here we describe the reconstitution of Pol ε-dependent MMR using S. cerevisiae proteins. A mixture of Msh2–Msh6 (or Msh2–Msh3), Exo1, RPA, RFC-Δ1N, PCNA, and Pol ε was found to catalyze both short-patch and long-patch 5′ nick-directed MMR of a substrate containing a +1 (+T) mispair. When the substrate contained a nick 3′ to the mispair, a mixture of Msh2–Msh6 (or Msh2–Msh3), Exo1, RPA, RFC-Δ1N, PCNA, and Pol ε was found to catalyze an MMR reaction that required Mlh1–Pms1. These results demonstrate that Pol ε can act in eukaryotic MMR in vitro.
关键词：mutator phenotype ; genome instability ; DNA replication fidelity ; DNA excision ; DNA repair
