Project description:Polycomb repressive complex 1 (PRC1) plays essential roles in cell fate determination. Recent studies have found that the composition of mammalian PRC1 is particularly varied and complicated, whereas the function of such variant PRC1 complexes on cell fate determination remains unknown. Here we show that Kdm2b, which recruits a variant PRC1 complex (PRC1.1) to CpG islands (CGIs), elevates Oct4 induced somatic reprogramming. Interaction with PRC1 is critical for Kdm2b’s promotion on the process of induced pluripotency. Furthermore, we find that bone morphogenetic proteins (BMPs) repress Oct4/Kdm2b induced somatic reprogramming selectively. Mechanistically, BMP-Smad pathway attenuates PRC1.1 occupation and H2AK119 ubiquitination on development genes, resulting in the release of meso-endoderm factors such as Sox17 and suppression of somatic reprogramming. These observations reveal that PRC1.1 participates in the establishment of pluripotency as well as cellular differentiation and identify BMP signal as a modulator of PRC1.1 function.
Project description:Polycomb repressive complex 1 (PRC1) plays essential roles in cell fate determination. Recent studies have found that the composition of mammalian PRC1 is particularly varied and complicated, whereas the function of such variant PRC1 complexes on cell fate determination remains unknown. Here we show that Kdm2b, which recruits a variant PRC1 complex (PRC1.1) to CpG islands (CGIs), elevates Oct4 induced somatic reprogramming. Interaction with PRC1 is critical for Kdm2b’s promotion on the process of induced pluripotency. Furthermore, we find that bone morphogenetic proteins (BMPs) repress Oct4/Kdm2b induced somatic reprogramming selectively. Mechanistically, BMP-Smad pathway attenuates PRC1.1 occupation and H2AK119 ubiquitination on development genes, resulting in the release of meso-endoderm factors such as Sox17 and suppression of somatic reprogramming. These observations reveal that PRC1.1 participates in the establishment of pluripotency as well as cellular differentiation and identify BMP signal as a modulator of PRC1.1 function.
Project description:The histone lysine demethylase protein, KDM2B, associates with the PCGF1/PRC1 complex and binds to non-methylated DNA through its ZF-CxxC domain, providing a possible molecular link between CpG island elements and polycomb nucleation (Farcas et al., 2012, Wu et al., 2013). Here, a novel genetic system was designed in which PCGF1/PRC1 targeting could be disrupted in vivo through the ablation of KDM2B-mediated DNA binding. To ablate PCGF1/PRC1 targeting, an exon that encodes most of the KDM2B ZF-CxxC domain and is shared by both the long and short form of the protein was flanked by loxP sites (Kdm2bfl/fl). Homozygous mouse ES cell lines were derived that also stably express a tamoxifen inducible form of CRE-recombinase. CRE induced deletion of the ZF-CxxC domain by the addition of tamoxifen yields KDM2B long and short form proteins that are incapable of binding to CpG island DNA but still remain associated with the PCGF1/PRC1 variant complex. We then assessed genome-wide occupancy of the PRC1 component RING1B and the PRC2 component SUZ12 to examine the impact of losing KDM2B-dependent targeting of polycomb. KDM2Bfl/fl ES cells were treated with 800M-BM-5M tamoxifen for 72hours and compared to untreated control cells by ChIP-seq for KDM2B, RING1B and SUZ12, and RNA-seq.
Project description:The chromatin modifying activities inherent to polycomb repressive complexes PRC1 and PRC2 play an essential role in gene regulation, cellular differentiation, and development. However, the mechanisms by which these complexes recognize their target sites and function together to form repressive chromatin domains remain poorly understood. Recruitment of PRC1 to target sites has been proposed to occur through a hierarchical process, dependent on the prior nucleation of PRC2 and placement of H3K27me3. Here, using a de novo targeting assay in mouse embryonic stem cells we unexpectedly discover that PRC1-dependent H2AK119ub1 leads to the recruitment of PRC2 and H3K27me3 to effectively initiate a polycomb domain. Genetic ablation of catalytic subunit of the PRC1 complex (RINGA/B) and ChIP-seq analysis of PRC1 and PRC2 components confirmed genome-wide decreases in PRC2 occupancy and H3K27me3 levels at PRC target sites. This activity is restricted to variant PRC1 complexes and genetic ablation experiments reveal that targeting of the variant PCGF1/PRC1 complex by KDM2B to CpG islands is required for polycomb domain formation and normal development. Together these observations provide a surprising new PRC1-dependent logic for PRC2 occupancy and polycomb domain formation. RING1A-/-;RING1Bfl/fl ES cells were treated with 800M-BM-5M tamoxifen for 48hours and compared to untreated control cells by ChIP-seq for RING1B, SUZ12, EZH2 and H3K27me3.
Project description:RNA-binding proteins (RBPs) are involved in a wide variety of regulatory pathways in mammalian cells. Here, we report that the DEAD-box RBP DDX5 (also known as p68) inhibits induced pluripotency by negatively regulating the expression and function of a non-canonical polycomb complex 1 (PRC1) subunit, RYBP, by modulating microRNA-125b processing. DDX5 loss-of-function, both during reprogramming and the somatic to pluripotent transition, and also in the differentiation of mouse embryonic stem cells, results in the suppression of lineage-specific genes via an RYBP-dependent ubiquitination of histone H2A at K119 (H2AK119ub1). RYBP functions as both transcriptional repressor through PRC1 but also as an activator through its interaction with OCT4 during reprogramming. Diminished DDX5 also potentiates RYBP-mediated recruitment of OCT4 to the promoter of the pluripotency activation gene Kdm2b. These data show that DDX5 down-regulation stimulates silencing of lineage-specific genes by RYBP-PRC1 in the early phase of reprogramming and activation of the pluripotency gene network by RYBP-OCT4 in the later phase of reprogramming.
Project description:RNA-binding proteins (RBPs) are involved in a wide variety of regulatory pathways in mammalian cells. Here, we report that the DEAD-box RBP DDX5 (also known as p68) inhibits induced pluripotency by negatively regulating the expression and function of a non-canonical polycomb complex 1 (PRC1) subunit, RYBP, by modulating microRNA-125b processing. DDX5 loss-of-function, both during reprogramming and the somatic to pluripotent transition, and also in the differentiation of mouse embryonic stem cells, results in the suppression of lineage-specific genes via an RYBP-dependent ubiquitination of histone H2A at K119 (H2AK119ub1). RYBP functions as both transcriptional repressor through PRC1 but also as an activator through its interaction with OCT4 during reprogramming. Diminished DDX5 also potentiates RYBP-mediated recruitment of OCT4 to the promoter of the pluripotency activation gene Kdm2b. These data show that DDX5 down-regulation stimulates silencing of lineage-specific genes by RYBP-PRC1 in the early phase of reprogramming and activation of the pluripotency gene network by RYBP-OCT4 in the later phase of reprogramming.
Project description:RNA-binding proteins (RBPs) are involved in a wide variety of regulatory pathways in mammalian cells. Here, we report that the DEAD-box RBP DDX5 (also known as p68) inhibits induced pluripotency by negatively regulating the expression and function of a non-canonical polycomb complex 1 (PRC1) subunit, RYBP, by modulating microRNA-125b processing. DDX5 loss-of-function, both during reprogramming and the somatic to pluripotent transition, and also in the differentiation of mouse embryonic stem cells, results in the suppression of lineage-specific genes via an RYBP-dependent ubiquitination of histone H2A at K119 (H2AK119ub1). RYBP functions as both transcriptional repressor through PRC1 but also as an activator through its interaction with OCT4 during reprogramming. Diminished DDX5 also potentiates RYBP-mediated recruitment of OCT4 to the promoter of the pluripotency activation gene Kdm2b. These data show that DDX5 down-regulation stimulates silencing of lineage-specific genes by RYBP-PRC1 in the early phase of reprogramming and activation of the pluripotency gene network by RYBP-OCT4 in the later phase of reprogramming.
Project description:The histone lysine demethylase protein, KDM2B, associates with the PCGF1/PRC1 complex and binds to non-methylated DNA through its ZF-CxxC domain, providing a possible molecular link between CpG island elements and polycomb nucleation (Farcas et al., 2012, Wu et al., 2013). Here, a novel genetic system was designed in which PCGF1/PRC1 targeting could be disrupted in vivo through the ablation of KDM2B-mediated DNA binding. To ablate PCGF1/PRC1 targeting, an exon that encodes most of the KDM2B ZF-CxxC domain and is shared by both the long and short form of the protein was flanked by loxP sites (Kdm2bfl/fl). Homozygous mouse ES cell lines were derived that also stably express a tamoxifen inducible form of CRE-recombinase. CRE induced deletion of the ZF-CxxC domain by the addition of tamoxifen yields KDM2B long and short form proteins that are incapable of binding to CpG island DNA but still remain associated with the PCGF1/PRC1 variant complex. We then assessed genome-wide occupancy of the PRC1 component RING1B and the PRC2 component SUZ12 to examine the impact of losing KDM2B-dependent targeting of polycomb.