Pax5 is required for recombination of transcribed, acetylated, 5' IgH V gene segments.
Pax5-deficient progenitor B (pro-B) cells are thought to be severely defective for recombination of all immunoglobulin heavy chain (IgH) V gene segments, but the mechanism by which Pax5 regulates this process has not been defined. To address this issue, we have examined the assembly of the IgH locus in Pax5-deficient pro-B cells and find, unexpectedly, that 3' IgH V gene segments, which lie closest to the D-J-Cmu region, recombine efficiently, but progressively more distal V gene segments recombine progressively less efficiently. Histone acetylation and germ-line transcription correlate strongly with an open or an accessible chromatin structure thought to be permissive for V(D)J recombination, and defects in recombination are typically accompanied by deficits in these processes. We were therefore surprised to observe that distal V(H) gene segments in Pax5-/- pro-B cells exhibit no defect in these measures of accessibility. The finding of transcribed, histone acetylated gene segments that fail to recombine suggests that a Pax5-dependent regulatory mechanism is required in addition to standard constraints of accessibility to control V(H) gene recombination.
Hesslein
David G T
DG
Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520-8011, USA.
Pflugh
David L
DL
Chowdhury
Dipanjan
D
Bothwell
Alfred L M
AL
Sen
Ranjan
R
Schatz
David G
DG
D000107:Acetylation; D000483:Alleles; D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism; D002843:Chromatin / Q000648:ultrastructure; D004254:DNA Nucleotidyltransferases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain / Q000502:physiology*; D005803:Genes, Immunoglobulin; D016654:Genes, RAG-1; D006657:Histones / Q000378:metabolism; D018398:Homeodomain Proteins / Q000502:physiology; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D051757:PAX5 Transcription Factor; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D045567:VDJ Recombinases
D002843:Chromatin; D004268:DNA-Binding Proteins; D006657:Histones; D018398:Homeodomain Proteins; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D051757:PAX5 Transcription Factor; C497282:Pax5 protein, mouse; D014157:Transcription Factors; C064658:RAG-1 protein; D004254:DNA Nucleotidyltransferases; D045567:VDJ Recombinases