Rad51 expression and localization in B cells carrying out class switch recombination.
Rad51 is a highly conserved eukaryotic homolog of the prokaryotic recombination protein RecA, which has been shown to function in both recombinational repair of DNA damage and meiotic recombination in yeast. In primary murine B cells cultured with lipopolysaccharide (LPS) to stimulate heavy chain class switch recombination, Rad51 protein levels are dramatically induced. Immunofluorescent microscopy shows that anti-Rad51 antibodies stain foci that are localized within the nuclei of switching B cells. Immunohistochemical analysis of splenic sections shows that clusters of cells that stain brightly with anti-Rad51 antibodies are evident within several days after primary immunization and that Rad51 staining in vivo is confined to B cells that are switching from expression of IgM to IgG antibodies. Following switch recombination, B cells populate splenic germinal centers, where somatic hypermutation and clonal proliferation occur. Germinal center B cells are not stained by anti-Rad51 antibodies. Rad51 expression is therefore not coincident with somatic hypermutation, nor does Rad51 expression correlate simply with cell proliferation. These data suggest that Rad51, or a highly related member of the conserved RecA family, may function in class switch recombination.
Li
M J
MJ
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA.
Peakman
M C
MC
Golub
E I
EI
Reddy
G
G
Ward
D C
DC
Radding
C M
CM
Maizels
N
N
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D002478:Cells, Cultured; D002874:Chromosome Mapping; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000032:analysis / Q000096:biosynthesis* / Q000276:immunology; D005455:Fluorescent Antibody Technique; D015870:Gene Expression; D005803:Genes, Immunoglobulin; D006801:Humans; D007114:Immunization; D017578:Immunoglobulin Class Switching / Q000187:drug effects; D007143:Immunoglobulin Heavy Chains / Q000096:biosynthesis / Q000235:genetics; D007150:Immunohistochemistry; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D051135:Rad51 Recombinase; D011994:Recombinant Proteins / Q000032:analysis / Q000276:immunology; D011995:Recombination, Genetic; D013154:Spleen / Q000276:immunology*; D013997:Time Factors
D000906:Antibodies; D004268:DNA-Binding Proteins; D007143:Immunoglobulin Heavy Chains; D008070:Lipopolysaccharides; D011994:Recombinant Proteins; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse