We have characterized extrachromosomal circular DNAs from adult mouse spleen cells that were induced to switch to immunoglobulin A (IgA) with bacterial lipopolysaccharide (LPS) and transforming growth factor beta (TGF-beta), and identified breakpoints of S mu/S gamma 3, S mu/S gamma 2, S mu/S alpha, S gamma 3/S alpha, and S gamma 2/S alpha recombinants. The S mu recombination donor sites clustered in the 3' half of the S mu region, while the S alpha recombination acceptor sites clustered in the 5' half of the S alpha region. In addition, donor and acceptor sites of S gamma regions also clustered in the 3' and 5' parts, respectively. These site preferences are in sharp contrast to the dispersed distribution of S mu/S gamma 1 breakpoints within both S mu and S gamma 1 regions upon IgG1 switch induced by LPS and interleukin 4. Our results support the hypotheses that TGF-beta increases the frequency of switch recombination events to IgA and that the switch recombination to IgA often proceeds by successive recombination of S mu/S gamma and S gamma/S alpha.
Biased distribution of recombination sites within S regions upon immunoglobulin class switch recombination induced by transforming growth factor beta and lipopolysaccharide.
T Iwasato, H Arakawa, A Shimizu, T Honjo, H Yamagishi; Biased distribution of recombination sites within S regions upon immunoglobulin class switch recombination induced by transforming growth factor beta and lipopolysaccharide.. J Exp Med 1 June 1992; 175 (6): 1539–1546. doi: https://doi.org/10.1084/jem.175.6.1539
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