G1 checkpoint is compromised in mouse ESCs due to functional uncoupling of p53-p21Waf1 signaling

• Published in: Cell cycle (Georgetown, Tex.) Vol. 15; no. 1; pp. 52 - 63
• Main Authors: Suvorova, Irina I., Grigorash, Bogdan B., Chuykin, Ilya A., Pospelova, Tatiana V., Pospelov, Valery A.
• Format: Journal Article
• Language: English
• Published: United States Taylor & Francis 02.01.2016
• Subjects: Animals; ATM/ATR signaling; checkpoint control; DNA damage; HDAC inhibitors; p53-p21/Waf1 pathway; proteasomal degradation; Cell Survival - physiology; Cyclin-Dependent Kinase Inhibitor p21 - metabolism; Embryonic Stem Cells - metabolism; G1 Phase Cell Cycle Checkpoints - physiology; Mice; NIH 3T3 Cells; Signal Transduction - physiology; Tumor Suppressor Protein p53 - metabolism; ATM/ATR signaling; checkpoint control; DNA damage; HDAC inhibitors; p53-p21/Waf1 pathway; proteasomal degradation
• ISSN: 1538-4101; 1551-4005; 1551-4005
• DOI: 10.1080/15384101.2015.1120927

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.