Larsen-Ledet Sven, Panfilova Aleksandra, Stein Amelie
Department of Biology, University of Copenhagen, Copenhagen, Denmark.
PLoS Genet. 2025 Apr 28;21(4):e1011681. doi: 10.1371/journal.pgen.1011681. eCollection 2025 Apr.
Missense mutations can have diverse effects on proteins, depending on their location within the protein and the specific amino acid substitution. Mutations in the DNA mismatch repair gene MLH1 are associated with Lynch syndrome, yet the underlying mechanism of most disease-causing mutations remains elusive. To address this gap, we aim to disentangle the mutational effects on two essential properties for MLH1 function: protein stability and protein-protein interaction. We systematically examine the cellular abundance and interaction with PMS2 of 4839 (94%) MLH1 variants in the C-terminal domain. Our combined data shows that most MLH1 variants lose interaction with PMS2 due to reduced cellular abundance. However, substitutions to charged residues in the canonical interface lead to reduced interaction with PMS2. Unexpectedly, we also identify a distal region in the C-terminal domain of MLH1 where substitutions cause both decreased and increased binding with PMS2, and propose a region in PMS2 as the binding site. Our data correlate with clinical classifications of benign and pathogenic MLH1 variants and align with thermodynamic stability predictions and evolutionary conservation. This work provides mechanistic insights into variant consequences and may help interpret MLH1 variants.
错义突变对蛋白质可能产生多种影响，这取决于它们在蛋白质中的位置以及具体的氨基酸替换。DNA错配修复基因MLH1中的突变与林奇综合征相关，但大多数致病突变的潜在机制仍不清楚。为了填补这一空白，我们旨在阐明突变对MLH1功能的两个基本特性的影响：蛋白质稳定性和蛋白质-蛋白质相互作用。我们系统地研究了C端结构域中4839个（94%）MLH1变体的细胞丰度以及与PMS2的相互作用。我们的综合数据表明，大多数MLH1变体由于细胞丰度降低而失去与PMS2的相互作用。然而，在经典界面中替换为带电荷的残基会导致与PMS2的相互作用减少。出乎意料的是，我们还在MLH1的C端结构域中确定了一个远端区域，其中的替换会导致与PMS2的结合减少和增加，并提出PMS2中的一个区域作为结合位点。我们的数据与MLH1良性和致病性变体的临床分类相关，并与热力学稳定性预测和进化保守性一致。这项工作为变体后果提供了机制性见解，可能有助于解释MLH1变体。
