The influence of transcriptional orientation on endogenous switch region function.
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(gamma1) region on CSR in vivo. Here we show that S(gamma1) is required for CSR, that CSR is effected by a 1-kilobase sequence that generates a G-rich transcript, and that inversion of S(gamma1) or the G-rich sequence decreases CSR. We conclude that S(gamma1) 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.
Shinkura
Reiko
R
Howard Hughes Medical Institute, The Children's Hospital, The Center for Blood Research, and Department of Genetics, Harvard University Medical School, Boston, MA 02115, USA.
Tian
Ming
M
Smith
Michele
M
Chua
Katrin
K
Fujiwara
Yuko
Y
Alt
Frederick W
FW
D000818:Animals; D001482:Base Composition; D001483:Base Sequence; D002678:Chimera; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000235:genetics; D007134:Immunoglobulin Switch Region; D051379:Mice; D008817:Mice, Mutant Strains; D008957:Models, Genetic; D018448:Models, Immunological; D009154:Mutation; D014158:Transcription, Genetic
D004277:DNA, Single-Stranded