Kruppel-like factor4 regulates PRDM1 expression through binding to an autoimmune risk allele
Su Hwa Jang, Helen Chen, Peter K. Gregersen, Betty Diamond, Sun Jung Kim
Su Hwa Jang, Helen Chen, Peter K. Gregersen, Betty Diamond, Sun Jung Kim
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Research Article

Kruppel-like factor4 regulates PRDM1 expression through binding to an autoimmune risk allele

Abstract

A SNP identified as rs548234, which is found in PRDM1, the gene that encodes BLIMP1, is a risk allele associated with systemic lupus erythematosus (SLE). BLIMP1 expression was reported to be decreased in women with the PRDM1 rs548234 risk allele compared with women with the nonrisk allele in monocyte-derived DCs (MO-DCs). In this study, we demonstrate that BLIMP1 expression is regulated by the binding of Kruppel-like factor 4 (KLF4) to the risk SNP. KLF4 is highly expressed in MO-DCs but undetectable in B cells, consistent with the lack of altered expression of BLIMP1 in B cells from risk SNP carriers. Female rs548234 risk allele carriers, but not nonrisk allele carriers, exhibited decreased levels of BLIMP1 in MO-DCs, showing that the regulatory function of KLF4 is influenced by the risk allele. In addition, KLF4 directly recruits histone deacetylases (HDAC4, HDAC6, and HDAC7), established negative regulators of gene expression. Finally, the knock down of KLF4 expression reversed the inhibitory effects of the risk SNP on promoter activity and BLIMP1 expression. Therefore, the binding of KLF4 and the subsequent recruitment of HDACs represent a mechanism for reduced BLIMP1 expression in MO-DCs bearing the SLE risk allele rs548234.

Authors

Su Hwa Jang, Helen Chen, Peter K. Gregersen, Betty Diamond, Sun Jung Kim

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Figure 6

Direct interaction between KLF4 and HDACs and recruitment of HDAC4 to rs548234 risk allele.

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Direct interaction between KLF4 and HDACs and recruitment of HDAC4 to rs...
Coimmunoprecipitation was performed with HEK293 cells (A) or MO-DCs (B) after KLF4 plasmid transfection. In both experiments, anti-KLF4 Ab or control Ab was incubated with total cell lysate overnight. Ab-protein complex was eluted, and Ab-bound proteins were separated by 4%–12% Bis-Tris protein gel. Untreated total input was loaded as a positive control. To detect HDACs, anti-HDAC antibodies were used. A representative image is shown from 3 independent experiments. (C) Recruitment of HDAC4 to the SNP region was measured by ChIP assay. Anti-HDAC4 Ab or control IgG was incubated with chromatin prepared from MO-DCs with the nonrisk control (T/T, white) or the risk (C/C, black) allele. Binding of HDAC4 to the SNP region was assessed by qPCR using SNP region-specific primers, and the percentage of input gDNA was calculated. Quantitation of the RECK promoter region was used as a positive control. In the box-and-whisker plot, horizontal bars indicate the medians, boxes indicate 25th to 75th percentiles, and whiskers indicate 10th and 90th percentiles (n = 4). The nonparametric, Mann-Whitney test was used for statistics.