Human MutS alpha mismatch repair complex (MutSα)

The human MutS alpha (hMutSα) mismatch repair complex is a heterodimeric protein assembly consisting of the MSH2 and MSH6 subunits (UniProt P43246, P52701). It serves as the primary sensor for DNA replication errors, specifically recognizing single base-base mismatches and small insertion-deletion loops (PubMed: 28100681). Upon recognition of a lesion, the complex utilizes its ATPase activity to undergo a conformational change into a sliding clamp, which then recruits the MutL alpha complex to initiate the excision and repair process (PubMed: 11557774). Deficiencies in hMutSα, resulting from germline mutations or epigenetic silencing, are the primary cause of Lynch syndrome and lead to a microsatellite instability-high (MSI-H) phenotype in various cancers (NIH: NBK1380). While hMutSα is not typically a direct target for inhibition, its functional status is a critical biomarker for the clinical use of immune checkpoint inhibitors like pembrolizumab and nivolumab, which are highly effective in MSI-H tumors (FDA: Pembrolizumab Label). Furthermore, recent therapeutic strategies focus on synthetic lethality, where the loss of hMutSα function renders cancer cells uniquely sensitive to the inhibition of the WRN helicase (PubMed: 31000590). This complex is thus central to both the maintenance of genomic integrity and the selection of modern precision oncology treatments.

Other names

MSH2-MSH6 complexhMutSαMutS alphaHuman MutS alphahMSH2-hMSH6

Recognition of DNA mismatches and small insertion-deletion loops followed by recruitment of MutLα to initiate repair (PubMed: 28100681). Deficiency in this complex leads to high mutational burden and neoantigen production, which sensitizes tumors to immune checkpoint inhibitors, or creates synthetic lethal dependencies on proteins like WRN helicase (PubMed: 31000590).