MSH3是抑癌基因，编码蛋白是MutS蛋白同源物3，参与DNA修复中的错配修复过程。MSH3与MSH2一起形成异源二聚体MutS-β，这对于识别和修复不匹配碱基对很重要，形成的DNA-MutS复合体可以向MMR机制中的其他组分发出信号以切除受损碱基。MSH3缺失或失去功能性突变可导致MMR缺陷，导致突变率增加。在几乎50%的MMR缺陷型的结直肠癌中MSH3发生体细胞移码突变。

MSH3 encodes the protein MutS Homolog 3 (MSH3) , the human homolog of the bacterial MutS protein, which functions in the mismatch repair (MMR) pathway of DNA repair. MSH3 partners with MSH2 to form the heterodimer MutS-beta, which is important for recognition and repair of mismatched base pairs, forming a DNA-MutS complex which signals other components of the MMR machinery to excise the aberrant nucleotide. MSH3 deletion or loss-of-function mutations can result in MMR deficiency, leading to an increased mutation rate and increased tumorigenesis in cooperation with loss of MSH6. MSH3 is altered in nearly 50% of MMR-deficient colorectal cancers by somatic frameshift mutations.

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