Multiple, conserved cryptic recombination signals in VH gene segments: detection of cleavage products only in pro B cells.
Receptor editing is believed to play the major role in purging newly formed B cell compartments of autoreactivity by the induction of secondary V(D)J rearrangements. In the process of immunoglobulin heavy (H) chain editing, these secondary rearrangements are mediated by direct V(H)-to-J(H) joining or cryptic recombination signals (cRSs) within V(H) gene segments. Using a statistical model of RS, we have identified potential cRSs within V(H) gene segments at conserved sites flanking complementarity-determining regions 1 and 2. These cRSs are active in extrachromosomal recombination assays and cleaved during normal B cell development. Cleavage of multiple V(H) cRSs was observed in the bone marrow of C57BL/6 and RAG2:GFP and microMT congenic animals, and we determined that cRS cleavage efficiencies are 30-50-fold lower than a physiological RS. cRS signal ends are abundant in pro-B cells, including those recovered from microMT mice, but undetectable in pre- or immature B cells. Thus, V(H) cRS cleavage regularly occurs before the generation of functional preBCR and BCR. Conservation of cRSs distal from the 3' end of V(H) gene segments suggests a function for these cryptic signals other than V(H) gene replacement.
Department of Immunology, Duke University, Durham, NC 27710, USA.
Marco
M
Davila
Feifei
F
Liu
Lindsay G
LG
Cowell
Anne E
AE
Lieberman
Emily
E
Heikamp
Anjali
A
Patel
Garnett
G
Kelsoe
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D001483:Base Sequence; D004268:DNA-Binding Proteins; D016368:Frameshift Mutation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008957:Models, Genetic; D008969:Molecular Sequence Data; D011336:Probability; D011995:Recombination, Genetic; D012984:Software
D000596:Amino Acids; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D007135:Immunoglobulin Variable Region; C499308:Rag2 protein, mouse; C064658:RAG-1 protein; D049452:Green Fluorescent Proteins