Branzei D, Seki M, Onoda F, Enomoto T
Molecular Cell Biology Laboratory, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, 980-8578, Japan.
Mol Genet Genomics. 2002 Nov;268(3):371-86. doi: 10.1007/s00438-002-0757-3. Epub 2002 Oct 8.
The Saccharomyces cerevisiae gene WHIP/ MGS1 encodes a protein related to the subunits of Replication Factor C (RFC). We found that the RFC-like motifs in Whip/Mgs1 are essential for its function. Furthermore, by screening for synthetic dosage lethality, we have shown that overexpression of MGS1 causes lethality in combination with mutations in genes that encode replication proteins such as DNA polymerase delta, RFC, PCNA and RPA. Moreover, loss of MGS1 function interferes with the ability of multicopy PCNA to suppress the replication defect of the rfc5-1 mutant. At permissive temperatures, deletion of MGS1 suppresses the hydroxyurea (HU) sensitivity of pol31 and pol32 mutants, which bear mutations in the smaller subunits of DNA polymerase delta, and at semipermissive and non-permissive temperatures mgs1delta partially alleviates the growth defects of the pol31 mutant. We also report that the growth defect and HU sensitivity of the pol31 mutant are suppressed by mms2delta and rad18delta mutations. We suggest that Mgs1 interacts with the DNA replication machinery to modulate the function of DNA polymerase delta during replication or replication-associated repair, and influences the choice of the pathway employed for replication fork reactivation. Possible roles of Mgs1, DNA polymerase delta, Rad18 and Mms2 in replication and replication fork restart are discussed.
酿酒酵母基因WHIP/MGS1编码一种与复制因子C（RFC）亚基相关的蛋白质。我们发现Whip/Mgs1中类RFC基序对其功能至关重要。此外，通过筛选合成剂量致死性，我们发现MGS1的过表达与编码复制蛋白（如DNA聚合酶δ、RFC、增殖细胞核抗原（PCNA）和复制蛋白A（RPA））的基因突变相结合会导致致死性。而且，MGS1功能的丧失会干扰多拷贝PCNA抑制rfc5-1突变体复制缺陷的能力。在允许温度下，缺失MGS1可抑制pol31和pol32突变体（它们在DNA聚合酶δ的较小亚基中发生突变）对羟基脲（HU）的敏感性，而在半允许温度和非允许温度下，mgs1Δ可部分缓解pol31突变体的生长缺陷。我们还报告说，mms2Δ和rad18Δ突变可抑制pol31突变体的生长缺陷和对HU的敏感性。我们认为Mgs1与DNA复制机制相互作用，在复制或复制相关修复过程中调节DNA聚合酶δ的功能，并影响用于复制叉重新激活的途径的选择。讨论了Mgs1、DNA聚合酶δ、Rad18和Mms2在复制和复制叉重启中的可能作用。
