Project description:Changing the somatic cell transcriptome to a pluripotent state using exogenous reprogramming factors needs transcriptional co-regulators that help activate or suppress gene expression and rewrite the epigenome. Here, we show that reprogramming-specific engagement of the NCoR/SMRT co-repressor complex at key pluripotency loci creates an epigenetic block to reprogramming. HDAC3 executes the repressive function of NCoR/SMRT in reprogramming by inducing histone deacetylation at these loci. Recruitment of NCoR/SMRT-HDAC3 to pluripotency genes is facilitated by all 4 Yamanaka factors (OCT4, SOX2, KLF4 and c-MYC) but mostly by c-MYC. Class IIa HDACs further potentiate this recruitment by interacting with both the reprogramming factors and NCoR/SMRT. Consequently, depleting NCoR/SMRT-HDAC3 function enables high efficiency of reprogramming, while elevating NCoR/SMRT-HDAC3 recruitment at pluripotency loci by over-expressing constitutively active class IIa HDACs derails it. Our findings thus uncover an unexpected epigenetic mechanism involving c-MYC, whose manipulation greatly enhances reprogramming efficiency.
Project description:The NCOR/SMRT corepressor complex is a fundamental coregulator of these mechanisms. However, the individual roles and the relative importance of the two major subunits NCOR and SMRT remain poorly understood. Here, we assessed the genome-wide roles of NCOR and SMRT in mouse macrophages by integrative analysis of cistrome, epigenome, and transcriptome. Although both corepressors exhibit genome-wide cooccupancy, their depletion revealed that SMRT primarily represses inflammation-related genes, whereas NCOR primarily represses metabolism-related genes. NCOR also activates inflammatory genes, some characteristic of tumor-associated macrophages. Corepressor depletion selectively alters chromatin accessibility, acetylation at enhancers, and the interplay with transcription factors. Both corepressors influence each other at chromatin, with SMRT superior to NCOR.
Project description:ChIP-seq of mouse embryonic fibroblast-adipose like cell line 3T3-L1 to identify binding sites of NCoR1 and SMRT following induction of differentiation, and RNA Pol-II after SMRT knock down
Project description:Changing the somatic cell transcriptome to a pluripotent state using exogenous reprogramming factors needs transcriptional co-regulators that help activate or suppress gene expression and rewrite the epigenome. Here, we show that reprogramming-specific engagement of the NCoR/SMRT co-repressor complex at key pluripotency loci creates an epigenetic block to reprogramming. HDAC3 executes the repressive function of NCoR/SMRT in reprogramming by inducing histone deacetylation at these loci. Recruitment of NCoR/SMRT-HDAC3 to pluripotency genes is facilitated by all 4 Yamanaka factors (OCT4, SOX2, KLF4 and c-MYC) but mostly by c-MYC. Class IIa HDACs further potentiate this recruitment by interacting with both the reprogramming factors and NCoR/SMRT. Consequently, depleting NCoR/SMRT-HDAC3 function enables high efficiency of reprogramming, while elevating NCoR/SMRT-HDAC3 recruitment at pluripotency loci by over-expressing constitutively active class IIa HDACs derails it. Our findings thus uncover an unexpected epigenetic mechanism involving c-MYC, whose manipulation greatly enhances reprogramming efficiency.
Project description:Using ChIP-seq, we reveal the SMRT and NCoR co-repressor cistromes, which each consist of over 30,000 half-shared binding sites. Moreover, we identify Bcl6-bound sub-cistromes for each co-repressor, which are strongly concentrated on NF-κB-driven inflammatory and tissue remodeling genes. These results reveal a critical role for Bcl6 and its corepressors SMRT and NCoR in the prevention of atherosclerosis and chronic inflammation. Identification of SMRT and NCoR binding sites in wild-type and Bcl6 knockout primary bone-marrow derived macrophages