Project description:Reactivation of the pluripotency network during somatic cell reprogramming by exogenous transcription factors involves chromatin remodeling and the recruitment of RNA polymerase II (Pol II) to target loci. Here, we report that Pol II is engaged at pluripotency promoters in reprogramming but remains paused and inefficiently released. We also show that bromodomain-containing protein 4 (BRD4) stimulates productive transcriptional elongation of pluripotency genes by dissociating the pause release factor P-TEFb from an inactive complex containing HEXIM1. Consequently, BRD4 overexpression enhances reprogramming efficiency and HEXIM1 suppresses it, whereas Brd4 and Hexim1 knockdown do the opposite. We further demonstrate that the reprogramming factor KLF4 helps recruit P-TEFb to pluripotency promoters. Our work thus provides a mechanism for explaining the reactivation of pluripotency genes in reprogramming and unveils an unanticipated role for KLF4 in transcriptional pause release. Pol II ChIP-seq for MEFs, ESCs and bulk populations of OSKM reprogramming intermediates at two time points.
Project description:Purposes: (1) compare the SUMO chromatin landscape between mouse embryonic fibroblasts (MEFs) and embryonic stem cells (ESc) (2) Decipher how hyposumoylation enhances MEF to induced pluripotent stem cells (iPSc) reprogramming (3) Decipher how hyposumoylation enhances ESc to 2C-like cells conversion. Methods : (1) ChIP-seq in MEFs and ESc for SUMO isoforms and histone marks. (2) ChIP-seq for transcription factors and histone marks at day 4 of MEF to iPSc reprogramming comparing wild type (shCtrl) and hyposumoylated cells (shUbc9). ATAC-Seq at day 4 of MEF to iPSc reprogramming comparing wild type (shCtrl) and hyposumoylated cells (shUbc9). RNA-Seq in MEFs, iPSc, at day 4 and day 7 of MEF to iPSc reprogramming comparing wild type (shCtrl) and hyposumoylated cells (shUbc9). (3) RNA-Seq in ESc comparing wild-type (siCtrl) and hyposumoylated cells (siUbc9). Results: (1) SUMO chromatin landscape is highly different between MEFs and ESc and associates to distinct chromatin marks. (2) Hyposumoylation enhances MEFs to iPSc reprogramming by favoring the extinction of the MEF transcriptional program and redistributing pluripotency factors from MEF enhancers toward ES enhancers. (3) Hyposumoylation enhances ES to 2C-like conversion by destabilizing heterochromatin thus resulting in an activation of the 2-cell transcriptional program. Conclusion: SUMO at chromatin is gate-keeper of cell-identity.
Project description:This SuperSeries is composed of the following subset Series: GSE30995: An Alternative Splicing Switch Regulates Embryonic Stem Cell Pluripotency and Reprogramming [RNA-Seq] GSE31006: An Alternative Splicing Switch Regulates Embryonic Stem Cell Pluripotency and Reprogramming [ChIP-Seq] GSE31007: An Alternative Splicing Switch Regulates Embryonic Stem Cell Pluripotency and Reprogramming [protein binding microarray] GSE31948: An Alternative Splicing Switch Regulates Embryonic Stem Cell Pluripotency and Reprogramming [AS microarray] Refer to individual Series
Project description:Reactivation of the pluripotency network during somatic cell reprogramming by exogenous transcription factors involves chromatin remodeling and the recruitment of RNA polymerase II (Pol II) to target loci. Here, we report that Pol II is engaged at pluripotency promoters in reprogramming but remains paused and inefficiently released. We also show that bromodomain-containing protein 4 (BRD4) stimulates productive transcriptional elongation of pluripotency genes by dissociating the pause release factor P-TEFb from an inactive complex containing HEXIM1. Consequently, BRD4 overexpression enhances reprogramming efficiency and HEXIM1 suppresses it, whereas Brd4 and Hexim1 knockdown do the opposite. We further demonstrate that the reprogramming factor KLF4 helps recruit P-TEFb to pluripotency promoters. Our work thus provides a mechanism for explaining the reactivation of pluripotency genes in reprogramming and unveils an unanticipated role for KLF4 in transcriptional pause release. Refer to individual Series