Kruppel-like factor4 regulates PRDM1 expression through binding to an autoimmune risk allele
Su Hwa Jang, … , Betty Diamond, Sun Jung Kim
Su Hwa Jang, … , Betty Diamond, Sun Jung Kim
Published January 12, 2017
Citation Information: JCI Insight. 2017;2(1):e89569. https://doi.org/10.1172/jci.insight.89569.
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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 2

KLF4 binds to the risk SNP.

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KLF4 binds to the risk SNP. (A) Schematic of genomic sequence around SNP...
(A) Schematic of genomic sequence around SNP rs548234. Putative binding sites of various transcription factors are found upstream and downstream of the SNP, and the KLF4-binding site is identified only in risk SNP by using Transfac and oPOSSUM 3.0 programs. (B) KLF binding with the risk allele probe (C/C) not with nonrisk allele probe (T/T) by EMSA. Recombinant KLF4 (left) or nuclear extract (NE) (5 μg) (right) was incubated with either T/T or C/C probe. To identify specificity of binding, either control or anti-KLF4 Ab was added. Arrows indicate KLF4 binding and asterisks indicate supershift. A representative image is shown from 3 independent experiments. (C) In vivo binding of KLF4 to the risk allele. To perform the ChIP assay, MO-DCs from either risk allele carriers (C/C) or nonrisk allele carriers (T/T) were prepared and incubated with either control goat IgG or anti-KLF Ab overnight. After precipitation, qPCR and PCR were performed with a primer set that amplifies the SNP region. The B2R gene was amplified as a positive control. Percentage of input was calculated relative level to the total input. 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.