Analysis of tandem E-box motifs within human Complement receptor 2 (CR2/CD21) promoter reveals cell specific roles for RP58, E2A, USF and localized chromatin accessibility

• Published in: The international journal of biochemistry & cell biology 2015-07, Vol.64, p.107-119
• Main Authors: Cruickshank, Mark N., Dods, James, Taylor, Rhonda L., Karimi, Mahdad, Fenwick, Emily J., Quail, Elizabeth A., Rea, Alexander J., Holers, V. Michael, Abraham, Lawrence J., Ulgiati, Daniela
• Format: Article
• Language: English
• Subjects: B cells; Base Sequence; Basic Helix-Loop-Helix Transcription Factors - physiology; Chromatin - physiology; E-Box Elements; Epigenesis, Genetic; Gene regulation; Human; Humans; K562 Cells; Molecular Sequence Data; Organ Specificity; Promoter Regions, Genetic; Receptors, Complement 3d - genetics; Receptors, Complement 3d - metabolism; Repressor Proteins - physiology; Transcription factors; Upstream Stimulatory Factors - metabolism
• ISSN: 1357-2725; 1878-5875
• DOI: 10.1016/j.biocel.2015.03.016

Complement receptor 2 (CR2/CD21) plays an important role in the generation of normal B cell immune responses. As transcription appears to be the prime mechanism via which surface CR2/CD21 expression is controlled, understanding transcriptional regulation of this gene will have broader implications to B cell biology. Here we report opposing, cell-context specific control of CR2/CD21 promoter activity by tandem E-box elements, spaced 22bp apart and within 70bp of the transcription initiation site. We have identified E2A and USF transcription factors as binding to the distal and proximal E-box sites respectively in CR2-positive B-cells, at a site that is hypersensitive to restriction enzyme digestion compared to non-expressing K562 cells. However, additional unidentified proteins have also been found to bind these functionally important elements. By utilizing a proteomics approach we have identified a repressor protein, RP58, binding the distal E-box motif. Co-transfection experiments using RP58 overexpression constructs demonstrated a specific 10-fold repression of CR2/CD21 transcriptional activity mediated through the distal E-box repressor element. Taken together, our results indicate that repression of the CR2/CD21 promoter can occur through one of the E-box motifs via recruitment of RP58 and other factors to bring about a silenced chromatin context within CR2/CD21 non-expressing cells.