Mismatch repair proteins MSH2, MLH1, and EXO1 are important for class-switch recombination events occurring in B cells that lack nonhomologous end joining.
In the absence of core nonhomologous end-joining (NHEJ) factors, Ab gene class-switch recombination (CSR) uses an alternative end-joining (A-EJ) pathway to recombine switch (S) region DNA breaks. Previous reports showing decreased S-junction microhomologies in MSH2-deficient mice and an exonuclease 1 (EXO1) role in yeast microhomology-mediated end joining suggest that mismatch repair (MMR) proteins might influence A-EJ-mediated CSR. We have directly investigated whether MMR proteins collectively or differentially influence the A-EJ mechanism of CSR by analyzing CSR in mice deficient in both XRCC4 and individual MMR proteins. We find CSR is reduced and that Igh locus chromosome breaks are reduced in the MMR/XRCC4 double-deficient B cells compared with B cells deficient in XRCC4 alone, suggesting MMR proteins function upstream of double-strand break formation to influence CSR efficiency in these cells. Our results show that MLH1, EXO1, and MSH2 are all important for efficient A-EJ-mediated CSR, and we propose that MMR proteins convert DNA nicks and point mutations into dsDNA breaks for both C-NHEJ and A-EJ pathways of CSR. We also find Mlh1-XRCC4(-) B cells have an increased frequency of direct S junctions, suggesting that MLH1 proteins may have additional functions that influence A-EJ-mediated CSR.
Department of Pathology, Tufts University School of Medicine, Boston, MA 02111, USA.
Jennifer
J
Eccleston
Catherine
C
Yan
Karen
K
Yuan
Frederick W
FW
Alt
Erik
E
Selsing
D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology*; D000818:Animals; D016175:B-Lymphocyte Subsets / Q000378:metabolism*; D002478:Cells, Cultured; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000172:deficiency* / Q000235:genetics; D015252:Deoxyribonucleases, Type II Site-Specific; D005090:Exodeoxyribonucleases / Q000502:physiology*; D017578:Immunoglobulin Class Switching / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000502:physiology*; D009687:Nuclear Proteins / Q000502:physiology*; D017354:Point Mutation
D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; C501485:Mlh1 protein, mouse; D009687:Nuclear Proteins; C519508:XLF protein, mouse; C511788:XRCC4 protein, mouse; D005090:Exodeoxyribonucleases; C028450:exodeoxyribonuclease I; C067043:endodeoxyribonuclease NheI; D015252:Deoxyribonucleases, Type II Site-Specific; C497173:Msh2 protein, mouse; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein
EMBO J. 1999 Jun 15;18(12):3484-90
10369687
J Exp Med. 2003 May 19;197(10):1291-6
12756266
Trends Genet. 2006 Jan;22(1):23-8
16309779
Nat Immunol. 2004 Feb;5(2):224-9
14716311
J Exp Med. 1999 Aug 2;190(3):323-30
10430621
Immunity. 2003 Oct;19(4):515-24
14563316
J Biol Chem. 1999 Jun 11;274(24):16894-900
10358035
Int Immunol. 1998 Jun;10(6):799-806
9678761
DNA Repair (Amst). 2009 Feb 1;8(2):242-52
19022408
J Exp Med. 2005 Jan 17;201(2):189-94
15657289
J Exp Med. 2004 Jul 5;200(1):61-8
15238605
Proc Natl Acad Sci U S A. 2009 Apr 7;106(14):5593-8
19307563
Nat Immunol. 2003 Oct;4(10):1023-8
12958596
Cell. 2006 Jul 28;126(2):297-308
16873062
J Exp Med. 2005 Feb 21;201(4):637-45
15710654
Proc Natl Acad Sci U S A. 2010 Feb 16;107(7):3034-9
20133803
Nature. 2003 Apr 17;422(6933):726-30
12692563
Mol Cell. 2004 Oct 22;16(2):163-71
15494304
Nucleic Acids Res. 1993 Feb 11;21(3):365-72
8441648
Annu Rev Biochem. 2005;74:681-710
15952900
Nature. 2002 Jul 4;418(6893):99-103
12097915
J Immunol. 2009 Jul 15;183(2):1222-8
19553545
J Exp Med. 2010 Feb 15;207(2):417-27
20142431
J Biol Chem. 1993 Jun 5;268(16):11838-44
8505312
J Immunol. 2007 Nov 1;179(9):6064-71
17947680
Cell. 2000 Sep 1;102(5):553-63
11007474
J Exp Med. 2007 Jul 9;204(7):1717-27
17606631
J Exp Med. 2002 Feb 4;195(3):367-73
11828012
EMBO J. 1987 Jun;6(6):1663-71
3038529
Mol Cell. 2006 Jan 20;21(2):201-14
16427010
Mol Cell. 2004 Jun 4;14(5):611-23
15175156
Curr Biol. 2002 Oct 15;12(20):1748-55
12401169
Proc Natl Acad Sci U S A. 2007 Dec 26;104(52):20902-7
18093953
Nucleic Acids Res. 1998 Dec 1;26(23):5333-42
9826756
Nature. 2007 Sep 27;449(7161):478-82
17713479
Nature. 2003 Jul 3;424(6944):103-7
12819663
Nat Genet. 1996 Jul;13(3):336-42
8673133
Proc Natl Acad Sci U S A. 2001 Dec 4;98(25):14553-8
11717399
Annu Rev Immunol. 2008;26:261-92
18370922
Genes Dev. 2003 Mar 1;17(5):603-14
12629043
Cell. 2000 Sep 1;102(5):565-75
11007475
J Exp Med. 2003 May 19;197(10):1377-83
12743174
Nat Genet. 1995 Sep;11(1):64-70
7550317
Nature. 1982 Mar 25;296(5855):325-31
6801527
J Exp Med. 2008 Nov 24;205(12):2745-53
19001141