R-loops at immunoglobulin class switch regions in the chromosomes of stimulated B cells.
The mechanism responsible for immunoglobulin class switch recombination is unknown. Previous work has shown that class switch sequences have the unusual property of forming RNA-DNA hybrids when transcribed in vitro. Here we show that the RNA-DNA hybrid structure that forms in vitro is an R-loop with a displaced guanine (G)-rich strand that is single-stranded. This R-loop structure exists in vivo in B cells that have been stimulated to transcribe the gamma3 or the gamma2b switch region. The length of the R-loops can exceed 1 kilobase. We propose that this distinctive DNA structure is important in the class switch recombination mechanism
Yu
Kefei
K
USC Norris Comprehensive Cancer Center, Room 5428, University of Southern California Keck School of Medicine, 1441 Eastlake Avenue, MC 9176, Los Angeles, CA 90033, USA.
Chedin
Frederic
F
Hsieh
Chih-Lin
CL
Wilson
Thomas E
TE
Lieber
Michael R
MR
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D001482:Base Composition; D002877:Chromosomes, Human / Q000235:genetics; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000235:genetics; D006801:Humans; D007134:Immunoglobulin Switch Region; D066298:In Vitro Techniques; D051379:Mice; D008957:Models, Genetic; D018448:Models, Immunological; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry / Q000235:genetics; D011995:Recombination, Genetic; D014158:Transcription, Genetic
D004277:DNA, Single-Stranded; D012313:RNA