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Mutations occur in the Ig Smu region but rarely in Sgamma regions prior to class switch recombination.


ABSTRACT: Nucleotide substitutions are found in recombined Ig switch (S) regions and also in unrecombined (germline, GL) Smicro segments in activated splenic B cells. Herein we examine whether mutations are also introduced into the downstream acceptor S regions prior to switch recombination, but find very few mutations in GL Sgamma3 and Sgamma1 regions in activated B cells. These data suggest that switch recombination initiates in the Smicro segment and secondarily involves the downstream acceptor S region. Furthermore, the pattern and specificity of mutations in GL and recombined Smicro segments differ, suggesting different repair mechanisms. Mutations in recombined Smicro regions show a strong bias toward G/C base pairs and WRCY/RGYW hotspots, whereas mutations introduced into the GL Smicro do not. Additionally, induction conditions affect mutation specificity within the GL Smicro segment. Mutations are most frequent near the S-S junctions and decrease rapidly with distance from the junction. Finally, we find that mice expressing a transgene for terminal deoxynucleotidyl transferase (TdT) have nucleotide insertions at S-S junctions, indicating that the recombining DNA ends are accessible to end-processing enzyme activities.

SUBMITTER: Schrader CE 

PROVIDER: S-EPMC275407 | biostudies-literature | 2003 Nov

REPOSITORIES: biostudies-literature

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Mutations occur in the Ig Smu region but rarely in Sgamma regions prior to class switch recombination.

Schrader Carol E CE   Bradley Sean P SP   Vardo Joycelyn J   Mochegova Sofia N SN   Flanagan Erin E   Stavnezer Janet J  

The EMBO journal 20031101 21


Nucleotide substitutions are found in recombined Ig switch (S) regions and also in unrecombined (germline, GL) Smicro segments in activated splenic B cells. Herein we examine whether mutations are also introduced into the downstream acceptor S regions prior to switch recombination, but find very few mutations in GL Sgamma3 and Sgamma1 regions in activated B cells. These data suggest that switch recombination initiates in the Smicro segment and secondarily involves the downstream acceptor S regio  ...[more]

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