Elements between the IgH variable (V) and diversity (D) clusters influence antisense transcription and lineage-specific V(D)J recombination.
Ig and T-cell receptor (TCR) variable-region gene exons are assembled from component variable (V), diversity (D) and joining (J) gene segments during early B and T cell development. The RAG1/2 endonuclease initiates V(D)J recombination by introducing DNA double-strand breaks at borders of the germ-line segments. In mice, the Ig heavy-chain (IgH) locus contains, from 5' to 3', several hundred V(H) gene segments, 13 D segments, and 4 J(H) segments within a several megabase region. In developing B cells, IgH variable-region exon assembly is ordered with D to J(H) rearrangement occurring on both alleles before appendage of a V(H) segment. Also, IgH V(H) to DJ(H) rearrangement does not occur in T cells, even though DJ(H) rearrangements occur at low levels. In these contexts, V(D)J recombination is controlled by modulating substrate gene segment accessibility to RAG1/2 activity. To elucidate control elements, we deleted the 100-kb intergenic region that separates the V(H) and D clusters (generating ΔV(H)-D alleles). In both B and T cells, ΔV(H)-D alleles initiated high-level antisense and, at lower levels, sense transcription from within the downstream D cluster, with antisense transcripts extending into proximal V(H) segments. In developing T lymphocytes, activated germ-line antisense transcription was accompanied by markedly increased IgH D-to-J(H) rearrangement and substantial V(H) to DJ(H) rearrangement of proximal IgH V(H) segments. Thus, the V(H)-D intergenic region, and likely elements within it, can influence silencing of sense and antisense germ-line transcription from the IgH D cluster and thereby influence targeting of V(D)J recombination.
Department of Genetics, The Howard Hughes Medical Institute, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Cosmas C
CC
Giallourakis
Andrew
A
Franklin
Chunguang
C
Guo
Hwei-Ling
HL
Cheng
Hye Suk
HS
Yoon
Michael
M
Gallagher
Thomas
T
Perlot
Milena
M
Andzelm
Andrew J
AJ
Murphy
Lynn E
LE
Macdonald
George D
GD
Yancopoulos
Frederick W
FW
Alt
D000483:Alleles; D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D021901:DNA, Intergenic / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain / Q000502:physiology*; D056426:Genetic Loci / Q000502:physiology; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D007143:Immunoglobulin Heavy Chains / Q000096:biosynthesis* / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008817:Mice, Mutant Strains; D016372:RNA, Antisense / Q000096:biosynthesis* / Q000235:genetics; D013601:T-Lymphocytes / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology*
D021901:DNA, Intergenic; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D016372:RNA, Antisense; C499308:Rag2 protein, mouse; C064658:RAG-1 protein