Multiple sequences from downstream of the J kappa cluster can combine to recruit somatic hypermutation to a heterologous, upstream mutation domain.
Recruitment of somatic hypermutation to the Ig kappa locus has previously been shown to depend on the enhancer elements, Ei/MAR and E3'. Here we show that these elements are not sufficient to confer mutability. However, hypermutation is effectively targeted to a chimeric beta-globin/Ig kappa transgene whose 5' end is composed of the human beta-globin gene (promoter and first two exons) and whose 3' end consists of selected sequences derived from downstream of the J kappa cluster (Ei/MAR, C kappa + flank and E3'). Thus, multiple downstream Ig kappa sequences (all derived from 3' of the J kappa cluster) can combine to recruit mutation to a heterologous mutation domain. The location of this hypermutation domain is defined by the position of the transcription start site and this applies even if the Ig kappa Ei/MAR is positioned upstream of the promoter. Hotspots within the mutation domain are, however, defined by local DNA sequence as evidenced by a new hotspot being created within the beta-globin domain by a mutation within the transgene. We propose that multiple, moveable Ig kappa sequences (that are normally located downstream of the transcription start site) cooperate to bring a hypermutation priming factor to the transcription initiation complex; a mutation domain is thereby created downstream of the promoter but the local sequence defines the detailed pattern of mutation within that domain.
Klix
N
N
Medical Research Council Laboratory of Molecular Biology, Cambridge, GB.
Jolly
C J
CJ
Davies
S L
SL
Brüggemann
M
M
Williams
G T
GT
Neuberger
M S
MS
D000818:Animals; D004742:Enhancer Elements, Genetic; D015322:Gene Rearrangement, B-Lymphocyte; D005803:Genes, Immunoglobulin; D007144:Immunoglobulin J-Chains / Q000235:genetics*; D007145:Immunoglobulin kappa-Chains / Q000235:genetics*; D008213:Lymphocyte Activation / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D009154:Mutation; D019076:Transgenes
D007144:Immunoglobulin J-Chains; D007145:Immunoglobulin kappa-Chains