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 3

Cell type–dependent expression of KLF4 and inverse correlation between BLIMP1 and KLF4.

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Cell type–dependent expression of KLF4 and inverse correlation between B...
(A) KLF4 mRNA (left) and KLF4 protein (right) were measured in MO-DCs and in total B cells. For mRNA, Each dot represents an individual sample, and the bar represents the mean ± SEM (n = 3). For protein, MO-DCs and total B cells were prepared, and 60 μg of total lysate was loaded for Western blotting. Actin is a loading control. A representative image is presented from 3 independent experiments. (B) The level of KLF4 mRNA was measured by qPCR and analyzed in risk allele carriers and control allele carriers: female (left) and male (right). Each dot represents an individual sample, and the bar represents the mean ± SEM (n = 10). (C) KLF4-expressing plasmid or control plasmid was transfected into MO-DCs prepared from nonrisk allele carriers or risk allele carriers. 48 hours after transfection, transfection efficiency was measured by GFP positivity and was around 60% in both control carriers and risk SNP carriers (top left). Total RNA was prepared, and mRNA levels of KLF4 (top right), BLIMP1 (middle row), and ATG5 (bottom row) were measured by qPCR. Relative expression was normalized to the level of HPRT1. 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 = 3). (D) KLF4 mRNA was measured in MO-DCs and human blood cDCs. Each dot represents an individual sample, and the bar represents the mean ± SEM (n = 4). The nonparametric, Mann-Whitney test was used for statistics.