부산대학교 도서관

Immunoglobulin heavy chain (IgH) class switch recombination (CSR) takes place between large switch (S) regions that precede exons of the constant region. The precise functions of the S region are controversial, although transcription of the S region targets CSR. We have tested the effects of deletion, inversion and replacement of the endogenous 12-kilobase S?1 region on CSR in vivo. Here we show that S?1 is required for CSR, that CSR is effected by a 1-kilobase sequence that generates a G-rich transcript, and that inversion of S?1 or the G-rich sequence decreases CSR. We conclude that S?1 function is dependent on orientation and lacks an absolute requirement for common S region motifs. We propose that single-stranded DNA stabilized by transcription-dependent, higher order structures is a primary substrate of CSR. [ABSTRACT FROM AUTHOR]