title: The influence of transcriptional orientation on endogenous switch region function.
abstract: 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.
authors.affiliation: 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.
authors.forename: Reiko
authors.initials: R
authors.lastname: Shinkura
authors.forename: Ming
authors.initials: M
authors.lastname: Tian
authors.forename: Michele
authors.initials: M
authors.lastname: Smith
authors.forename: Katrin
authors.initials: K
authors.lastname: Chua
authors.forename: Yuko
authors.initials: Y
authors.lastname: Fujiwara
authors.forename: Frederick W
authors.initials: FW
authors.lastname: Alt
mesh_terms: 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
chemical_list: D004277:DNA, Single-Stranded