Goethe University Frankfurt, University Hospital, Medical Clinic 1, Biomedical Research Laboratory, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany.
Sci Rep. 2023 Aug 2;13(1):12503. doi: 10.1038/s41598-023-39750-x.
MutLα is essential for human DNA mismatch repair (MMR). It harbors a latent endonuclease, is responsible for recruitment of process associated proteins and is relevant for strand discrimination. Recently, we demonstrated that the MMR function of MutLα is regulated by phosphorylation of MLH1 at serine (S) 477. In the current study, we focused on S87 located in the ATPase domain of MLH1 and on S446, S456 and S477 located in its linker region. We analysed the phosphorylation-dependent impact of these amino acids on DNA binding, MMR ability and thermal stability of MutLα. We were able to demonstrate that phosphorylation at S87 of MLH1 inhibits DNA binding of MutLα. In addition, we detected that its MMR function seems to be regulated predominantly via phosphorylation of serines in the linker domain, which are also partially involved in the regulation of DNA binding. Furthermore, we found that the thermal stability of MutLα decreased in relation to its phosphorylation status implying that complete phosphorylation might lead to instability and degradation of MLH1. In summary, we showed here, for the first time, a phosphorylation-dependent regulation of DNA binding of MutLα and hypothesized that this might significantly impact its functional regulation during MMR in vivo.
MutLα 对于人类 DNA 错配修复 (MMR) 是必不可少的。它含有一个潜伏的内切酶，负责招募与过程相关的蛋白质，并与链区分有关。最近，我们证明了 MutLα 的 MMR 功能受到 MLH1 丝氨酸 (S) 477 磷酸化的调节。在本研究中，我们专注于 MLH1 的 ATP 酶结构域中的 S87 以及其连接区域中的 S446、S456 和 S477。我们分析了这些氨基酸的磷酸化依赖性对 MutLα 的 DNA 结合、MMR 能力和热稳定性的影响。我们能够证明 MLH1 的 S87 磷酸化抑制 MutLα 的 DNA 结合。此外，我们发现其 MMR 功能似乎主要通过连接区域中丝氨酸的磷酸化来调节，这些丝氨酸也部分参与 DNA 结合的调节。此外，我们发现 MutLα 的热稳定性与其磷酸化状态有关，这表明完全磷酸化可能导致 MLH1 的不稳定性和降解。总之，我们首次展示了 MutLα 的 DNA 结合的磷酸化依赖性调节，并假设这可能会显著影响其在体内 MMR 过程中的功能调节。
