MSH2-MSH6 stimulates DNA polymerase eta, suggesting a role for A:T mutations in antibody genes.
Activation-induced cytidine deaminase deaminates cytosine to uracil (dU) in DNA, which leads to mutations at C:G basepairs in immunoglobulin genes during somatic hypermutation. The mechanism that generates mutations at A:T basepairs, however, remains unclear. It appears to require the MSH2-MSH6 mismatch repair heterodimer and DNA polymerase (pol) eta, as mutations of A:T are decreased in mice and humans lacking these proteins. Here, we demonstrate that these proteins interact physically and functionally. First, we show that MSH2-MSH6 binds to a U:G mismatch but not to other DNA intermediates produced during base excision repair of dUs, including an abasic site and a deoxyribose phosphate group. Second, MSH2 binds to pol eta in solution, and endogenous MSH2 associates with the pol in cell extracts. Third, MSH2-MSH6 stimulates the catalytic activity of pol eta in vitro. These observations suggest that the interaction between MSH2-MSH6 and DNA pol eta stimulates synthesis of mutations at bases located downstream of the initial dU lesion, including A:T pairs.
Wilson
Teresa M
TM
Radiation Oncology Research Laboratory, Department of Radiation Oncology, University of Maryland, Baltimore, MD 21201, USA.
Vaisman
Alexandra
A
Martomo
Stella A
SA
Sullivan
Patsa
P
Lan
Li
L
Hanaoka
Fumio
F
Yasui
Akira
A
Woodgate
Roger
R
Gearhart
Patricia J
PJ
D020137:Base Pair Mismatch; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051718:MutS Homolog 2 Protein; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D027041:Somatic Hypermutation, Immunoglobulin
D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; D011518:Proto-Oncogene Proteins; D004259:DNA-Directed DNA Polymerase; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein