title: G1 checkpoint is compromised in mouse ESCs due to functional uncoupling of p53-p21Waf1 signaling.
abstract: Mouse embryonic stem cells (mESCs) lack of G1 checkpoint despite that irradiation (IR) activates ATM/ATR-mediated DDR signaling pathway. The IR-induced p53 localizes in the nuclei and up-regulates p21/Waf1 transcription but that does not lead to accumulation of p21/Waf1 protein. The negative control of the p21Waf1 expression appears to occur at 2 levels of regulation. First, both p21/Waf1 gene transcription and the p21/Waf1 protein content increase in mESCs treated with histone-deacetylase inhibitors, implying its epigenetic regulation. Second, proteasome inhibitors cause the p21/Waf1 accumulation, indicating that the protein is a subject of proteasome-dependent degradation in ESСs. Then, the dynamics of IR-induced p21Waf1 protein show its accumulation at long-term time points (3 and 5 days) that coincides with an increase in the proportion of G1-phase cells, down-regulation of Oct4 and Nanog pluripotent gene transcription and activation of endoderm-specific genes sox17 and afp. In addition, nutlin-dependent stabilization of p53 in mESC was also accompanied by the accumulation of p21/Waf1 as well as restoration of G1 checkpoint and an onset of differentiation. Thus, the lack of functional p21/Waf1 is indispensable for maintaining self-renewal and pluripotency of mESCs.
authors.affiliation: a Institute of Cytology , Russian Academy of Sciences , St-Petersburg , Russia.|b Saint-Petersburg State University, Saint-Petersburg State University , St-Petersburg , Russia.
authors.forename: Irina I
authors.initials: II
authors.lastname: Suvorova
authors.affiliation: a Institute of Cytology , Russian Academy of Sciences , St-Petersburg , Russia.|b Saint-Petersburg State University, Saint-Petersburg State University , St-Petersburg , Russia.
authors.forename: Bogdan B
authors.initials: BB
authors.lastname: Grigorash
authors.affiliation: c Mount Sinai School of Medicine , New York , NY , USA.
authors.forename: Ilya A
authors.initials: IA
authors.lastname: Chuykin
authors.affiliation: a Institute of Cytology , Russian Academy of Sciences , St-Petersburg , Russia.|b Saint-Petersburg State University, Saint-Petersburg State University , St-Petersburg , Russia.
authors.forename: Tatiana V
authors.initials: TV
authors.lastname: Pospelova
authors.affiliation: a Institute of Cytology , Russian Academy of Sciences , St-Petersburg , Russia.|b Saint-Petersburg State University, Saint-Petersburg State University , St-Petersburg , Russia.
authors.forename: Valery A
authors.initials: VA
authors.lastname: Pospelov
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000502:physiology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D053595:Embryonic Stem Cells / Q000378:metabolism*; D059585:G1 Phase Cell Cycle Checkpoints / Q000502:physiology*; D051379:Mice; D041681:NIH 3T3 Cells; D015398:Signal Transduction / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016159:Tumor Suppressor Protein p53
keywords: ATM/ATR signaling; checkpoint control; DNA damage; HDAC inhibitors; p53-p21/Waf1 pathway; proteasomal degradation