title: An intronic silencer regulates B lymphocyte cell- and stage-specific expression of the human complement receptor type 2 (CR2, CD21) gene.
abstract: Human CR2 (CD21) is a B lymphocyte protein whose surface expression is restricted primarily to the mature cell stage during development. To study the transcriptional mechanisms that govern cell- and stage-restricted CR2 expression, we first performed transient transfection analysis using constructs extending from -5 kb to +75 bp (-5 kb/+75) in the CR2 promoter. The promoter was found to be broadly active, with no evidence of cell- or stage-specific reporter gene expression. However, the addition of a 2.5-kb intronic gene segment (containing a DNase I hypersensitive site) to the (-5-kb/+75) construct resulted in appropriate reporter gene expression, defined as the silencing of the (-5-kb/+75) promoter activity only in non-CR2-expressing cells. Interestingly, appropriate reporter gene expression required stable transfection of the constructs in cell lines, suggesting nuclear matrix or chromatin interactions may be important for appropriate CR2 gene expression. Importantly, transgenic mice also required the intronic silencer to generate lymphoid tissue-specific reporter gene expression. Some transgenic founder lines did not demonstrate reporter gene expression, however, indicating that additional transcriptional regulatory elements are present in other regions of the CR2 gene. In summary, these data support the hypothesis that human CR2 expression is regulated primarily by an intronic silencer with lineage- and B cell stage-specific activity.
authors.affiliation: Department of Medicine, University of Colorado Health Sciences Center, Denver 80262, USA.
authors.forename: K W
authors.initials: KW
authors.lastname: Makar
authors.forename: C T
authors.initials: CT
authors.lastname: Pham
authors.forename: M H
authors.initials: MH
authors.lastname: Dehoff
authors.forename: S M
authors.initials: SM
authors.lastname: O'Connor
authors.forename: S M
authors.initials: SM
authors.lastname: Jacobi
authors.forename: V M
authors.initials: VM
authors.lastname: Holers
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D003850:Deoxyribonuclease I / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D007438:Introns / Q000276:immunology*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000235:genetics / Q000276:immunology; D012333:RNA, Messenger / Q000096:biosynthesis; D017464:Receptors, Complement 3d / Q000096:biosynthesis / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid / Q000276:immunology*; D014158:Transcription, Genetic / Q000276:immunology
chemical_list: D012333:RNA, Messenger; D017464:Receptors, Complement 3d; D003850:Deoxyribonuclease I