Institute of Biochemistry II, Goethe University Medical School, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany.
Mol Cell. 2010 Feb 12;37(3):396-407. doi: 10.1016/j.molcel.2009.12.039.
DNA polymerase eta is a Y family polymerase involved in translesion synthesis (TLS). Its action is initiated by simultaneous interaction between the PIP box in pol eta and PCNA and between the UBZ in pol eta and monoubiquitin attached to PCNA. Whereas monoubiquitination of PCNA is required for its interaction with pol eta during TLS, we now show that monoubiquitination of pol eta inhibits this interaction, preventing its functions in undamaged cells. Identification of monoubiquitination sites within pol eta nuclear localization signal (NLS) led to the discovery that pol eta NLS directly contacts PCNA, forming an extended pol eta-PCNA interaction surface. We name this the PCNA-interacting region (PIR) and show that its monoubiquitination is downregulated by various DNA-damaging agents. We propose that this mechanism ensures optimal availability of nonubiquitinated, TLS-competent pol eta after DNA damage. Our work shows how monoubiquitination can either positively or negatively regulate the assembly of a protein complex, depending on which substrates are targeted by ubiquitin.
DNA 聚合酶 eta 是一种参与跨损伤合成 (TLS) 的 Y 家族聚合酶。它的作用是通过 pol eta 中的 PIP 盒与 PCNA 以及 pol eta 中的 UBZ 与连接到 PCNA 的单泛素同时相互作用而启动的。虽然 PCNA 的单泛素化是其与 pol eta 在 TLS 期间相互作用所必需的，但我们现在表明，pol eta 的单泛素化抑制了这种相互作用，从而阻止了其在未受损细胞中的功能。在 pol eta 核定位信号 (NLS) 内鉴定出单泛素化位点，导致发现 pol eta NLS 直接与 PCNA 接触，形成扩展的 pol eta-PCNA 相互作用表面。我们将其命名为 PCNA 相互作用区域 (PIR)，并表明各种 DNA 损伤剂可下调其单泛素化。我们提出，这种机制可确保在 DNA 损伤后非泛素化的、具有 TLS 功能的 pol eta 最佳可用。我们的工作表明，单泛素化可以根据泛素的靶向底物，正向或负向调节蛋白质复合物的组装。
