Mutations occur in the Ig S  region but rarely in S  regions prior to class switch recombination

摘要: Nucleotide substitutions are found in recombined Ig switch (S) regions and also unrecombined (germline, GL) Sµ segments activated splenic B cells. Herein we examine whether mutations introduced into the downstream acceptor S prior to recombination, but find very few GL Sγ3 Sγ1 These data suggest that recombination initiates segment secondarily involves region. Furthermore, pattern specificity of differ, suggesting different repair mechanisms. Mutations show a strong bias toward G/C base pairs WRCY/RGYW hotspots, whereas do not. Additionally, induction conditions affect mutation within segment. most frequent near S–S junctions decrease rapidly with distance from junction. Finally, mice expressing transgene for terminal deoxynucleotidyl transferase (TdT) have nucleotide insertions at junctions, indicating recombining DNA ends accessible end-processing enzyme activities.