Project description:Ubiquitination-mediated protein degradation of key transcriptional factors is important to the self-renewal of embryonic stem (ES) cells. However, little is known about the deubiquitination in ES self-renewal and differentiation. Here, we report that deubiquitinase USP21 is an important positive regulator to keep ES cells under undifferentiation stasus by deubiquitination and stabilization of Nanog, a key transcriptional factor of ES cells. Loss of USP21 led to ES cells differentiation and defect in reprogramming.
Project description:Nanog is a master pluripotency factor of embryonic stem cells (ESCs). Stable expression of Nanog is required to maintain the stemness of ESCs, although Nanog is a short-lived protein and quickly degraded by the ubiquitin-dependent proteasome system (UPS). Here, we report that the deubiquitinase USP21 interacts with, deubiquitinates and stabilizes Nanog and therefore maintains the protein level of Nanog in mouse-ESCs (mESCs). Loss of USP21 results in Nanog destruction, mESCs differentiation and reduced the somatic cell reprogramming efficiency. USP21 is a transcriptional target of the LIF/STAT3 pathway and is downregulated upon differentiation. Moreover, differentiation cues promote ERK-mediated phosphorylation and dissociation of USP21 from Nanog, thus leading to Nanog degradation. Additionally, USP21 is recruited to gene promoters by Nanog to deubiquitinate histone H2A at K119 and thus facilitates Nanog-mediated gene expression. Together, our findings provide a regulatory mechanism by which extrinsic signals regulate mESC fate via deubiquitinating Nanog.
Project description:TAF4 directed immunoprecipitation of the the Pre-initiation complex from mouse embryonic stem cells with or without depletion of TATA-box binding protein (TBP).
Project description:Protein kinase signalling is a major mechanism by which embryonic stem cell pluripotency and differentiation is controlled. However, the pathways and components that regulate embryonic stem cell identity have not been systematically defined. Here, we employ FGF4 signalling as a model system to investigate phosphoproteome dynamics in differentiating mouse embryonic stem cells. We report identification and quantitation of more than 10,000 phosphopeptides, of which hundreds of phosphophoylation sites are regulated more than 2-fold by acute FGF4 stimulation. We hypothesise that phosphorylation sites in this dataset are relevant for regulating the transition of mouse embryonic stem cells from pluripotency towards lineage specific differentiation.