Northam Matthew R, Garg Parie, Baitin Dmitri M, Burgers Peter M J, Shcherbakova Polina V
Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA.
EMBO J. 2006 Sep 20;25(18):4316-25. doi: 10.1038/sj.emboj.7601320. Epub 2006 Sep 7.
DNA polymerase zeta (Polzeta) participates in translesion DNA synthesis and is involved in the generation of the majority of mutations induced by DNA damage. The mechanisms that license access of Polzeta to the primer terminus and regulate the extent of its participation in genome replication are poorly understood. The Polzeta-dependent damage-induced mutagenesis requires monoubiquitination of proliferating cell nuclear antigen (PCNA) that is triggered by exposure to mutagens. We show that Polzeta contributes to DNA replication and causes mutagenesis not only in response to DNA damage but also in response to malfunction of normal replicative machinery due to mutations in replication genes. These replication defects lead to ubiquitination of PCNA even in the absence of DNA damage. Unlike damage-induced mutagenesis, the Polzeta-dependent spontaneous mutagenesis in replication mutants is reduced in strains defective in both ubiquitination and sumoylation of Lys164 of PCNA. Additionally, studies of a PCNA mutant defective for functional interactions with Polzeta, but not for monoubiquitination by the Rad6/Rad18 complex demonstrate a role for PCNA in regulating the mutagenic activity of Polzeta separate from its modification at Lys164.
DNA聚合酶ζ（Polζ）参与跨损伤DNA合成，并与DNA损伤诱导的大多数突变的产生有关。目前对于允许Polζ接近引物末端并调节其参与基因组复制程度的机制了解甚少。依赖Polζ的损伤诱导诱变需要增殖细胞核抗原（PCNA）的单泛素化，这是由暴露于诱变剂触发的。我们发现，Polζ不仅在响应DNA损伤时，而且在由于复制基因中的突变导致正常复制机制出现故障时，都对DNA复制有贡献并导致诱变。这些复制缺陷即使在没有DNA损伤的情况下也会导致PCNA的泛素化。与损伤诱导的诱变不同，复制突变体中依赖Polζ的自发诱变在PCNA Lys164泛素化和SUMO化均有缺陷的菌株中减少。此外，对与Polζ功能相互作用有缺陷但不影响Rad6/Rad18复合物单泛素化的PCNA突变体的研究表明，PCNA在调节Polζ的诱变活性方面具有独立于其在Lys164修饰的作用。
