Different mutation signatures in DNA polymerase eta- and MSH6-deficient mice suggest separate roles in antibody diversification.
Hypermutation in immunoglobulin genes produces a high frequency of substitutions of all four bases, which are likely generated by low-fidelity DNA polymerases. Indeed, humans deficient for DNA polymerase (pol) eta have decreased substitutions of A.T base pairs in variable and switch regions. To study the role of pol eta in a genetically tractable system, we created mice lacking pol eta. B cells from Polh-/- mice produced normal amounts of IgG, indicating that pol eta does not affect class switch recombination. Similar to their human counterparts, variable and switch regions from Polh-/- mice had fewer substitutions of A.T base pairs and correspondingly more mutations of C.G base pairs, which firmly establishes a central role for pol eta in hypermutation. Notably, the location and types of substitutions differ markedly from those in Msh6-/- clones, which also have fewer A.T mutations. The data suggest that pol eta preferentially synthesizes a repair patch on the nontranscribed strand, whereas MSH6 functions to generate the patch.
Martomo
Stella A
SA
Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
Yang
William W
WW
Wersto
Robert P
RP
Ohkumo
Tsuyoshi
T
Kondo
Yuji
Y
Yokoi
Masayuki
M
Masutani
Chikahide
C
Hanaoka
Fumio
F
Gearhart
Patricia J
PJ
D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism; D004252:DNA Mutational Analysis; D017931:DNA Primers; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D004259:DNA-Directed DNA Polymerase / Q000235:genetics*; D005434:Flow Cytometry; D017578:Immunoglobulin Class Switching / Q000235:genetics*; D007074:Immunoglobulin G / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation / Q000235:genetics*; D000099270:Y-Family DNA Polymerases
D017931:DNA Primers; D004268:DNA-Binding Proteins; D004259:DNA-Directed DNA Polymerase; D007074:Immunoglobulin G; C102997:Msh6 protein, mouse; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases