DHFR/MSH3 amplification in methotrexate-resistant cells alters the hMutSalpha/hMutSbeta ratio and reduces the efficiency of base-base mismatch repair.


Journal Article

The level and fate of hMSH3 (human MutS homolog 3) were examined in the promyelocytic leukemia cell line HL-60 and its methotrexate-resistant derivative HL-60R, which is drug resistant by virtue of an amplification event that spans the dihydrofolate reductase (DHFR) and MSH3 genes. Nuclear extracts from HL-60 and HL-60R cells were subjected to an identical, rapid purification protocol that efficiently captures heterodimeric hMutSalpha (hMSH2. hMSH6) and hMutSbeta (hMSH2.hMSH3). In HL-60 extracts the hMutSalpha to hMutSbeta ratio is roughly 6:1, whereas in methotrexate-resistant HL-60R cells the ratio is less than 1:100, due to overproduction of hMSH3 and heterodimer formation of this protein with virtually all the nuclear hMSH2. This shift is associated with marked reduction in the efficiency of base-base mismatch and hypermutability at the hypoxanthine phosphoribosyltransferase (HPRT) locus. Purified hMutSalpha and hMutSbeta display partial overlap in mismatch repair specificity: both participate in repair of a dinucleotide insertion-deletion heterology, but only hMutSalpha restores base-base mismatch repair to extracts of HL-60R cells or hMSH2-deficient LoVo colorectal tumor cells.

Full Text

Duke Authors

Cited Authors

  • Drummond, JT; Genschel, J; Wolf, E; Modrich, P

Published Date

  • September 16, 1997

Published In

Volume / Issue

  • 94 / 19

Start / End Page

  • 10144 - 10149

PubMed ID

  • 9294177

Pubmed Central ID

  • 9294177

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.94.19.10144


  • eng

Conference Location

  • United States