Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
Mol Cell. 2010 Feb 12;37(3):408-17. doi: 10.1016/j.molcel.2009.12.038.
Translesion synthesis is an essential cell survival strategy to promote replication after DNA damage. The accumulation of Y family polymerases (pol) iota and Rev1 at the stalled replication machinery is mediated by the ubiquitin-binding motifs (UBMs) of the polymerases and enhanced by PCNA monoubiquitination. We report the solution structures of the C-terminal UBM of human pol iota and its complex with ubiquitin. Distinct from other ubiquitin-binding domains, the UBM binds to the hydrophobic surface of ubiquitin centered at L8. Accordingly, mutation of L8A, but not I44A, of ubiquitin abolishes UBM binding. Human pol iota contains two functional UBMs, both contributing to replication foci formation. In contrast, only the second UBM of Saccharomyces cerevisiae Rev1 binds to ubiquitin and is essential for Rev1-dependent cell survival and mutagenesis. Point mutations disrupting the UBM-ubiquitin interaction also impair the accumulation of pol iota in replication foci and Rev1-mediated DNA damage tolerance in vivo.
跨损伤合成是一种重要的细胞生存策略，可促进 DNA 损伤后的复制。Y 家族聚合酶（pol）iota 和 Rev1 在停滞的复制机制中的积累是由聚合酶的泛素结合基序（UBM）介导的，并通过 PCNA 单泛素化增强。我们报告了人 pol iota 的 C 末端 UBM 及其与泛素复合物的溶液结构。与其他泛素结合结构域不同，UBM 结合到以 L8 为中心的泛素疏水面上。因此，泛素 L8A 的突变，而不是 I44A 的突变，会破坏 UBM 结合。人 pol iota 包含两个功能 UBM，都有助于复制焦点的形成。相比之下，只有酿酒酵母 Rev1 的第二个 UBM 与泛素结合，对于 Rev1 依赖的细胞存活和诱变至关重要。破坏 UBM-泛素相互作用的点突变也会损害 pol iota 在复制焦点中的积累和 Rev1 介导的体内 DNA 损伤耐受。
