Project description:Chromatin protein positive coactivator 4 (PC4) has multiple functions, including chromatin compaction. However, its role in immune cells is largely unknown. We show that PC4 orchestrates chromatin structure and gene expression in mature B cells. B-cell specific PC4-deficient mice showed impaired production of antibody upon antigen stimulation. The PC4 complex purified from B cells contained transcription factors IKAROS and IRF4. IKAROS protein was reduced in PC4-deficient mature B cells, resulting in de-repression of their target genes in part by diminished interactions with gene silencing components. Upon activation, IRF4 protein amount was not increased in PC4-deficient B cells, resulting in reduction of plasma cells. Importantly, IRF4 reciprocally induced PC4 expression via a super-enhancer. PC4 knockdown in human B-cell lymphoma cells reduced IKAROS protein as an anticancer drug lenalidomide. Our findings establish PC4 as a chromatin regulator of B cells and a possible therapeutic target adjoining IKAROS in B-cell malignancies.
Project description:B cell development is orchestrated by various transcription factors collaborating with chromatin remodelers that determine the genomic architecture. However, chromatin regulation in mature B cells is still poorly understood. Here, we show the critical function of positive coactivator 4 (PC4), a bona fide non-histone chromatin protein encoded by Sub1. B-cell specific Sub1-deficient mice showed the decreased number and response against antigen stimulation of mature B cells. By combining PC4 chromatin immunoprecipitation-sequencing and complex purification, we identified transcription factor IKAROS as a partner of PC4 in gene regulation. PC4 and IKAROS cooperated to promote heterochromatin formation of their target gene loci and thereby established B cell identity. Importantly, PC4 stabilized IKAROS protein in mature B cells and inhibited IKAROS degradation by the anti-cancer drug lenalidomide in human B-cell lymphoma cells. These findings establish PC4 as not only a chromatin regulator of B cells but also a new therapeutic target in B-cell malignancies.
Project description:B cell development is orchestrated by various transcription factors collaborating with chromatin remodelers that determine the genomic architecture. However, chromatin regulation in mature B cells is still poorly understood. Here, we show the critical function of positive coactivator 4 (PC4), a bona fide non-histone chromatin protein encoded by Sub1. B-cell specific Sub1-deficient mice showed the decreased number and response against antigen stimulation of mature B cells. By combining PC4 chromatin immunoprecipitation-sequencing and complex purification, we identified transcription factor IKAROS as a partner of PC4 in gene regulation. PC4 and IKAROS cooperated to promote heterochromatin formation of their target gene loci and thereby established B cell identity. Importantly, PC4 stabilized IKAROS protein in mature B cells and inhibited IKAROS degradation by the anti-cancer drug lenalidomide in human B-cell lymphoma cells. These findings establish PC4 as not only a chromatin regulator of B cells but also a new therapeutic target in B-cell malignancies.
Project description:To assess the mechanisms by which PC4 mediates chromatin compaction in cells and regulation of genome organization by its phosphorylation state, we measured the chromatin accessibility landscape using ATAC-seq of vector control 293 cells (Control/shNS), PC4 knockdown (KD/PC4 KD) and upon ectopic expression of Flag tagged PC4 (FP/PC4), Phosphomimic-PC4 (PM/PM-PC4) and phospho-mutant (MTP/MTP5) in PC4 knockdown cells.
Project description:To investigate the binding site in which PC4 protein association with its target RNAs. eCLIP-seq was performed to profile PC4-binding RNA targets in Huh7 cells.
Project description:In order to get an idea of involvement of PC4 in regulation of p53-dependent gene expression, we carried out global gene expression profiling upon treatment with R6-NLS-p53(380–386-3Ac). R6-NLS-p53(380–386-3Ac) is a small peptide of 20 residues derived from p53 C-terminal domain. This peptide can successfully block the cellular p53-PC4 interactions. Lung cancer line A549 which contain both wild type p53 and PC4 were used for this study. The cells were treated with 25µM R6-NLS-p53(380–386-3Ac) for two different time points (12 h and 24 h) and the gene expression profile was analyzed by microarray analysis.