title: Characterization of the proximal enhancer element and transcriptional regulatory factors for murine recombination activating gene-2.
abstract: Recombination-activating gene (RAG)-1 and RAG-2 are essential for V(D)J recombination and are expressed specifically in lymphoid cells. We previously identified two putative enhancer elements, the proximal and distal enhancers, located at -2.6 and -8 kb, respectively, 5' upstream of mouse RAG-2, and characterized the distal enhancer element in detail. In this study, to characterize the proximal enhancer in vitro as well as in vivo, we first defined a 170-bp core enhancer element within the proximal enhancer (Ep) and determined its activity in various cells. Ep conferred enhancer activity only in B-lymphoid cell lines, but not in T- or non-lymphoid cell lines. Analysis of the transgenic mice carrying an EGFP reporter gene linked with Ep revealed that Ep activated the transcription of the reporter gene in bone marrow and spleen, but not in thymus or non-lymphoid tissues. Ep was active in both B220+IgM- and B220+IgM+ subpopulations in the bone marrow and in the B220+ subpopulation in the spleen. Using electrophoretic mobility shift assays and mutational assays, we found that Ikaros and CCAAT/enhancer binding protein cooperatively bind Ep and function as the transcription factors responsible for B cell-specific enhancer activity. These results demonstrate the role of Ep as a cis-regulatory enhancer element for RAG-2-specific expression in B-lymphoid lineages.
authors.affiliation: Department of Immunology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Sugitani, Toyama, Japan.
authors.forename: Xing-Cheng
authors.initials: XC
authors.lastname: Wei
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Dohkan
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kishi
authors.forename: Chun-Xiao
authors.initials: CX
authors.lastname: Wu
authors.forename: Sachiko
authors.initials: S
authors.lastname: Kondo
authors.forename: Atsushi
authors.initials: A
authors.lastname: Muraguchi
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D001483:Base Sequence; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation / Q000502:physiology*; D017930:Genes, Reporter; D051740:Ikaros Transcription Factor; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; C499308:Rag2 protein, mouse; D014157:Transcription Factors; C064655:V(D)J recombination activating protein 2; C497238:Zfpn1a1 protein, mouse; D051740:Ikaros Transcription Factor