The human PMS2L proteins do not interact with hMLH1, a major DNA mismatch repair protein

The human PMS2 gene encodes one of the bacterial mutL homologs that is associated with hereditary nonpolyposis colorectal cancer (HNPCC). One of the interesting features of the hPMS2 gene is that it is part of a multiple gene family which is localized on chromosome bands 7p22, 7p12-p13, 7q11, and 7q22. Here we report four newly identified hPMS2-like (PMS2L) genes. All four novel members of the PMS2L gene family encode relatively short polypeptides composed of the amino-terminal portion of hPMS2 and are expressed ubiquitously except in the heart. To clarify whether the PMS2L polypeptides contribute to the DNA mismatch repair (MMR) pathway through an interaction with hMLH1, we have performed a yeast two-hybrid assay and an immunoprecipitation study using an hPMS2 mutant cell line, HEC-1-A. Our results clearly indicate that hMLH1 does not interact with two representative PMS2Ls, whereas the carboxyl-terminal portion of hPMS2, not the amino-terminal portion, does interact with hMLH1. Thus, PMS2Ls are not likely to participate in the MMR pathway through association with hMLH1; they must play some other roles in the living cells.