The DNA mismatch repair gene hMSH2 is a potent coactivator of oestrogen receptor α

The DNA mismatch repair gene is a key regulator in the elimination of base–base mismatches and insertion/deletion loops (IDLs). Human MutS homologue 2 (hMSH2), originally identified as a human homologue of the bacterial MutS, is a tumour suppressor gene frequently mutated in hereditary nonpolyposis colorectal cancer. Hereditary nonpolyposis colorectal cancer is characterised by the early onset of colorectal cancer and the development of extracolonic cancers such as endometrial, ovarian, and urological cancers. Oestrogen receptor (ER) α and β are members of a nuclear receptor (NR) superfamily. Ligand-dependent transcription of ER is regulated by the p160 steroid receptor coactivator family, the thyroid hormone receptor-associated proteins/the vitamin D receptor-interacting proteins (TRAP/DRIP) mediator complex, and the TATA box-binding protein (TBP)-free TBP associated factor complex (TFTC) type histone acetyltransferase complex. Here, we report the interaction between ER α/β and hMSH2. Immunoprecipitation and glutathione-S-transferase pulldown assay revealed that ER α and hMSH2 interacted in a ligand-dependent manner, whereas ER β and hMSH2 interacted in a ligand-independent manner. Oestrogen receptor α/β bound to hMSH2 through the hMSH3/hMSH6 interaction domain of hMSH2. In a transient expression assay, hMSH2 potentiated the transactivation function of liganded ER α, but not that of ER β. These results suggest that hMSH2 may play an important role as a putative coactivator in ER α dependent gene expression.