title: Detection and characterization of R-loops at the murine immunoglobulin Sα region.
abstract: IgA is the most abundant antibody in mammals. However, the mechanism of its class switching is still not clear. The formation of the R-loops, as the target for AID, has been proposed to play a crucial role during mammalian class switch recombination. Here, we provide a systematic evaluation of R-loops at Sα (IgA) in CH12F3-2A cells, which is a unique cell model system for class switch recombination because of its consistent switching to IgA upon stimulation. The results of R-loop analysis demonstrate distinct features specific to Sα. Some R-loops may initiate from the end of Iα, but all terminate exclusively within Sα. Time-course analysis also indicates that the percentage of R-loops peaks prior to the occurrence of class switch recombination. This is the first demonstration that R-loops form at Sαin vitro and in situ, despite variable G density and relatively few GGGG clusters in Sα. The short distance from the promoter to Sα may compensate for the less robust R-loop-forming factors at Sα relative to other switch regions. In conclusion, R-loops at the Sα region further support R-loop formation as a general feature of all stimulated switch regions.
authors.affiliation: Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei, Taiwan.
authors.forename: Yu-Pu
authors.initials: YP
authors.lastname: Kao
authors.forename: Wen-Chuan
authors.initials: WC
authors.lastname: Hsieh
authors.forename: Shu-Ting
authors.initials: ST
authors.lastname: Hung
authors.forename: Chiun-Wei
authors.initials: CW
authors.lastname: Huang
authors.forename: Michael R
authors.initials: MR
authors.lastname: Lieber
authors.forename: Feng-Ting
authors.initials: FT
authors.lastname: Huang
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D019295:Computational Biology / Q000379:methods; D007070:Immunoglobulin A / Q000235:genetics; D017578:Immunoglobulin Class Switching / Q000235:genetics*; D007134:Immunoglobulin Switch Region / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D060152:V(D)J Recombination
chemical_list: D007070:Immunoglobulin A