BCL-6 suppresses miR-142-3p/5p expression in SLE CD4+ T cells by modulating histone methylation and acetylation of the miR-142 promoter

The reduced expression of miR-142-3p/5p in CD4+ T cells of SLE patients caused T cell hyperactivity and B cell hyperstimulation. This study aimed to investigate the mechanisms of regulating miR-142-3p/5p expression in SLE CD4+ T cells. The BCL-6 expression was significantly increased in SLE CD4+ T cells compared with normal controls, and the BCL-6 expression was inversely correlated with miR-142-3p/5p expression. BCL-6 suppresses the expression of miR-142-3p/5p by increasing H3K27me3 level and reducing H3K9/K14ac levels in SLE CD4+ T cells. BCL-6 regulates histone modifications in miR-142 promoter by recruiting EZH2 and HDAC5. Furthermore, we observed significantly decreased CD40L, ICOS, and IL-21 expression levels in SLE CD4+ T cells with BCL-6 interference, and obviously reduced autoantibody IgG production in autologous B cells co-cultured with BCL-6 inhibited SLE CD4+ T cells. Our study found that increased BCL-6 up-regulates H3K27me3 and down-regulates H3K9/14ac at miR-142 promoter in SLE CD4+ T cells. These factors induce a declination in miR-142-3p/5p expression, consequently resulting in CD4+ T cell hyperactivity.