HDAC1 epigenetically regulates IRF4 expression by fine-tuning histone acetylation in MM cells. (A) HDAC1 enrichment around H3K27Ac sites (left) and RNA Pol II binding sites (right) for all genes was analyzed using publicly available ChIP-seq data (GSM2302869 [HDAC1], GSM894083 [H3K27Ac], and GSM1070127 [RNA Pol II]). Heatmaps of HDAC1 levels at H3K27Ac sites or RNA Pol II-binding sites in MM.1S cells are shown (bottom). Each row indicated ±5 kb centered on the H3K27Ac or RNA Pol II sites. The mean signal in the same intervals is plotted (top). (B) RNA-seq data of HDAC1-knockdown RPMI 8226 cells (supplemental Table 1) allocated HDAC1-related (violet dots) and -nonrelated (gray dots) genes based on ChIP-seq data (GSM2302869). Genes shown as a volcano plot selected based on fold changes (x-axis) with adjusted P (y-axis). (C) The distribution of HDAC1, H3K27Ac, and RNA Pol II binding at the IRF4 locus in MM.1S cells was analyzed (GSM2302869 [HDAC1], GSM894083 [H3K27Ac], and GSM1070127 [RNA Pol II]). The x-axis shows the genomic position. (D-E) MM.1S and RPMI 8226 cells were treated with 1 μM of MS-275 for 24 hours and were then subjected to ChIP-Q-PCR for (D) H3K27Ac levels around the IRF4 gene or (E) RNA Pol II binding around the TSS of the IRF4 gene. Results were normalized to control immunoglobulin G (IgG) in each gene position. Error bars show the SD of triplicates. ∗∗P < .01, ∗∗∗P < .001 significantly different from the condition without MS-275 at each gene position; the Student t test. Ns, not significant.