A cis-acting diversification activator both necessary and sufficient for AID-mediated hypermutation.
Hypermutation of the immunoglobulin (Ig) genes requires Activation Induced cytidine Deaminase (AID) and transcription, but it remains unclear why other transcribed genes of B cells do not mutate. We describe a reporter transgene crippled by hypermutation when inserted into or near the Ig light chain (IgL) locus of the DT40 B cell line yet stably expressed when inserted into other chromosomal positions. Step-wise deletions of the IgL locus revealed that a sequence extending for 9.8 kilobases downstream of the IgL transcription start site confers the hypermutation activity. This sequence, named DIVAC for diversification activator, efficiently activates hypermutation when inserted at non-Ig loci. The results significantly extend previously reported findings on AID-mediated gene diversification. They show by both deletion and insertion analyses that cis-acting sequences predispose neighboring transcription units to hypermutation.
Blagodatski
Artem
A
Institute for Molecular Radiobiology, Helmholtz Center Munich, Neuherberg, Germany.
Batrak
Vera
V
Schmidl
Sabine
S
Schoetz
Ulrike
U
Caldwell
Randolph B
RB
Arakawa
Hiroshi
H
Buerstedde
Jean-Marie
JM
D000818:Animals; D001402:B-Lymphocytes; D002645:Chickens; D002874:Chromosome Mapping; D003564:Cytidine Deaminase / Q000378:metabolism*; D005434:Flow Cytometry; D017353:Gene Deletion; D005786:Gene Expression Regulation; D050439:Genes, Immunoglobulin Light Chain; D017930:Genes, Reporter; D014644:Genetic Variation; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D012045:Regulatory Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA; D027041:Somatic Hypermutation, Immunoglobulin; D014162:Transfection; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
D049452:Green Fluorescent Proteins; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase