NF-κB Regulates the Expression of the Human Complement Receptor 2 Gene

Abstract

CR2 is a key regulator of the B cell response to Ag. Here we show that NF-κB enhances the expression of the human CR2 gene. Promoter truncation, deletion, and mutagenesis studies indicated a functional role for a consensus NF-κB promoter element, as well as a heterogeneous nuclear ribonucleoprotein D element and an overlapping X box/E box. By supershift analysis, the first two elements bound NF-κB p50 and p65 and heterogeneous nuclear ribonucleoprotein RNP D, respectively. The X box/E box bound regulatory factor X5 and, surprisingly, NF-κB p50 and p65. Overexpression of NF-κB p50 enhanced the activity of the CR2 promoter in B cell lines and primary B cells, suggesting a direct role for NF-κB in regulating promoter activity. Importantly, mutation of the NF-κB element or the X box/E box rendered the promoter unresponsive to NF-κB p50. Using chromatin immunoprecipitation in live B cell lines and primary B cells, we found that NF-κB proteins p50, p65, and c-Rel bound to the genomic promoter at two locations that overlap with the consensus NF-κB element or the X box/E box. Finally, stimuli that activate NF-κB enhanced the activity of the CR2 promoter, and LPS rapidly increased the number of CR2 proteins on the surface of primary B cells. We propose that the NF-κB signaling pathway enhances the expression of the CR2 gene, as a result of NF-κB proteins binding to two CR2 promoter elements. Thus, at the onset of an infection, LPS could sensitize the B cell to Ag by enhancing the level of CR2-costimulatory molecules on the cell surface.

A Novel Mechanism of Alternative Promoter and Splicing Regulates the Epitope Generation of Tumor Antigen CML66-L

“…3, C and D, the representative results from the experiments repeated four times showed that the 1.8-kb CML66-L promoter in the sense orientation had strong promoter activities compared with the antisense-oriented CML66-L promoter control and the no-insert vector control in both Hela cells and HCCT cells (not shown). The strength of sense-oriented CML66-L promoter was in a level equivalent to that of SV40 promoter in pGL-3 Control vector (the positive control, not shown) (22,23). In contrast, CML66-S promoter in the sense orientation had much low promoter activities in comparison to that of CML66-L promoter in Hela cells and HCCT cells.…”

Association of a common complement receptor 2 haplotype with increased risk of systemic lupus erythematosus

“…The human CR2 gene (OMIM 120650) encodes a membrane glycoprotein, consisting of 15 repeating structures termed short consensus repeats (SCRs), that is expressed on mature B cells and follicular dendritic cells, as well as an alternatively spliced 16 SCR variant that is expressed primarily on follicular dendritic cells (13). Its relative expression is primarily controlled at the level of transcription by the proximal promoter (14)(15)(16)(17), and cell and lineage specificity of expression is regulated by an intronic silencer (18,19). CR2 binds C3 degradation products covalently bound to antigen in the process of complement activation, as well as EBV (20), the immunomodulatory protein CD23 (21), and IFN-␣ (22).…”

Defining In Vivo Transcription Factor Complexes of the Murine CD21 and CD23 Genes

“…Both genes have been found to be controlled, via reporter assays, by two distinct regions of the gene: the proximal promoter regions and sequences within the first intron. The human CD21 gene has been shown to possess a number of functional sites, including Sp1, AP1, AP2, and E box sites proximal to the TATA box sequence, and NF-B and heterogeneous ribonucleoprotein sites further upstream (Ϫ531 and Ϫ495 relative to the transcription induction site, respectively) (13)(14)(15)(16)(17)(18)(19). The mouse CD21 promoter possesses a functional Oct-1 site (equal binding via EMSA with T and B cell nuclear extracts), a consensus Pax5 binding site (showing a B cell-specific EMSA pattern), and a conserved NF-B site (also showing equal binding via EMSA with T and B cell nuclear extracts) all within the first 280 bp of the promoter region (7, 20 -22).…”