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
View: Text | PDF
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

×

Figure 5

Knockdown of KLF4 abolished the regulatory effect by risk allele.

Options: View larger image (or click on image) Download as PowerPoint
Knockdown of KLF4 abolished the regulatory effect by risk allele. (A) KL...
(A) KLF4 knockdown by shRNA. Four different KLF4-targeting shRNA constructs (A, B, C, and C) and scrambled control shRNA lentivirus were infected into THP-1 cells. Four days after two rounds of infection, shRNA-positive cells were purified based on GFP expression (red box with asterisk). Cells with each construct were harvested, and mRNA and protein levels were measured by qPCR and Western blotting, respectively. Whisker plot represents the mean to max (n = 3). The Western blot image is representative of 3 experiments. (B) Promoter assay was performed in KLF4dl THP-1 cells. Each plasmid was transfected into either control shRNA or KLF4 shRNA (KLF4dl) as shown in figure, and luciferase activity was measured. 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). (C) MO-DCs from control or risk allele carriers were infected with control shRNA or KLF4 shRNA lentivirus at day 5 and day 7 during differentiation. Four days after the second infection (day 9), GFP-positive MO-DCs were sorted and the level of KLF4 and BLIMP1 was measured by qPCR. Each dot represents an individual sample (n = 4). The nonparametric, Mann-Whitney test was used for statistics.