Nucleic Acids Research, Vol 24, Issue 11 2104-2111, Copyright © 1996 by Oxford University Press
J Li, GA Daniels and MR Lieber
Junctions at class switch recombination sites in the genome are
characterized by a unique sequence feature. Nucleotide substitutions and
small deletions are common on either of the two sides of the switch
junction, but not on both together. We have previously reported an
extrachromosomal substrate assay system for analyzing the recombination of
class switch sequences. Here we have sequenced nine junctions on each side
of the break point and compared these to 17 recombination junctions of
control substrates from the same cells. Five of the nine switch
recombination junctions have nucleotide substitutions and deletions, with
multiple nucleotide changes being more common. Furthermore, mutations were
found only on a single side of the junction, just as for the recombination
of switch sequences in the genome. In contrast, only one of 17 control
substrate junctions had a mutation, and this was a single nucleotide
insertion. This difference is highly significant (P < 0.00007) and
indicates that the fundamental recombination mechanism is likely to be
similar for switch sequences in the chromosome and on minichromosome
substrates.
ARTICLES
Asymmetric mutation around the recombination break point of immunoglobulin class switch sequences on extrachromosomal substrates
Division of Molecular Oncology, and Center for Immunology, Washington University School of Medicine, St Louis, MO 63110, USA.
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