Glaab WE, Risinger JI, Umar A, Kunkel TA, Barrett JC, Tindall KR. Characterization of distinct human endometrial carcinoma cell lines deficient in mismatch repair that originated from a single tumor.
J Biol Chem 1998;
273:26662-9. [PMID:
9756907 DOI:
10.1074/jbc.273.41.26662]
[Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The role of specific mismatch repair (MMR) gene products was examined by observing several phenotypic end points in two MMR-deficient human endometrial carcinoma cell lines that were originally isolated from the same tumor. The first cell line, HEC-1-A, contains a nonsense mutation in the hPMS2 gene, which results in premature termination and a truncated hPMS2 protein. In addition, HEC-1-A cells carry a splice mutation in the hMSH6 gene and lack wild-type hMSH6 protein. The second cell line, HEC-1-B, possesses the same defective hMSH6 locus. However, HEC-1-B cells are heterozygous at the hPMS2 locus; that is, along with carrying the same nonsense mutation in hPMS2 as in HEC-1-A, HEC-1-B cells also contain a wild-type hPMS2 gene. Initial recognition of mismatches in DNA requires either the hMSH2/hMSH6 or hMSH2/hMSH3 heterodimer, with hPMS2 functioning downstream of damage recognition. Therefore, cells defective in hPMS2 should completely lack MMR (HEC-1-A), whereas cells mutant in hMSH6 only (HEC-1-B) can potentially repair damage via the hMSH2/hMSH3 heterodimer. The data presented here in HEC-1-B cells illustrate (i) the reduction of instability at microsatellite sequences, (ii) a significant decrease in frameshift mutation rate at HPRT, and (iii) the in vitro repair of looped substrates, relative to HEC-1-A cells, illustrating the repair of frameshift intermediates by hMSH2/hMSH3 heterodimer. Furthermore, the role of hMSH2/hMSH3 heterodimer in the repair of base:base mismatches is supported by observing the reduction in base substitution mutation rate at HPRT in HEC-1-B cells (hMSH6-defective but possessing wild-type hPMS2), as compared with HEC-1-A (hMSH6/hPMS2-defective) cells. These data support a critical role for hPMS2 in human MMR, while further defining the role of the hMSH2/hMSH3 heterodimer in maintaining genomic stability in the absence of a wild-type hMSH2/hMSH6 heterodimer.
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