NF-kappaB regulates the expression of the human complement receptor 2 gene.
CR2 is a key regulator of the B cell response to Ag. Here we show that NF-kappaB enhances the expression of the human CR2 gene. Promoter truncation, deletion, and mutagenesis studies indicated a functional role for a consensus NF-kappaB 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-kappaB p50 and p65 and heterogeneous nuclear ribonucleoprotein RNP D, respectively. The X box/E box bound regulatory factor X5 and, surprisingly, NF-kappaB p50 and p65. Overexpression of NF-kappaB p50 enhanced the activity of the CR2 promoter in B cell lines and primary B cells, suggesting a direct role for NF-kappaB in regulating promoter activity. Importantly, mutation of the NF-kappaB element or the X box/E box rendered the promoter unresponsive to NF-kappaB p50. Using chromatin immunoprecipitation in live B cell lines and primary B cells, we found that NF-kappaB proteins p50, p65, and c-Rel bound to the genomic promoter at two locations that overlap with the consensus NF-kappaB element or the X box/E box. Finally, stimuli that activate NF-kappaB 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-kappaB signaling pathway enhances the expression of the CR2 gene, as a result of NF-kappaB 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.
Tolnay
Mate
M
Department of Cellular Injury, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA. mtolnay@hotmail.com
Vereshchagina
Lyudmila A
LA
Tsokos
George C
GC
D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit; D011401:Promoter Regions, Genetic; D017464:Receptors, Complement 3d / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D051996:Transcription Factor RelA
D008070:Lipopolysaccharides; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D017464:Receptors, Complement 3d; D051996:Transcription Factor RelA; D004247:DNA