title: p53 regulates cell cycle and microRNAs to promote differentiation of human embryonic stem cells.
abstract: Multiple studies show that tumor suppressor p53 is a barrier to dedifferentiation; whether this is strictly due to repression of proliferation remains a subject of debate. Here, we show that p53 plays an active role in promoting differentiation of human embryonic stem cells (hESCs) and opposing self-renewal by regulation of specific target genes and microRNAs. In contrast to mouse embryonic stem cells, p53 in hESCs is maintained at low levels in the nucleus, albeit in a deacetylated, inactive state. In response to retinoic acid, CBP/p300 acetylates p53 at lysine 373, which leads to dissociation from E3-ubiquitin ligases HDM2 and TRIM24. Stabilized p53 binds CDKN1A to establish a G(1) phase of cell cycle without activation of cell death pathways. In parallel, p53 activates expression of miR-34a and miR-145, which in turn repress stem cell factors OCT4, KLF4, LIN28A, and SOX2 and prevent backsliding to pluripotency. Induction of p53 levels is a key step: RNA-interference-mediated knockdown of p53 delays differentiation, whereas depletion of negative regulators of p53 or ectopic expression of p53 yields spontaneous differentiation of hESCs, independently of retinoic acid. Ectopic expression of p53R175H, a mutated form of p53 that does not bind DNA or regulate transcription, failed to induce differentiation. These studies underscore the importance of a p53-regulated network in determining the human stem cell state.
authors.affiliation: Program in Genes and Development, Center for Stem Cell and Development Biology, Department of Biochemistry and Molecular Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Abhinav K
authors.initials: AK
authors.lastname: Jain
authors.forename: Kendra
authors.initials: K
authors.lastname: Allton
authors.forename: Michelina
authors.initials: M
authors.lastname: Iacovino
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Mahen
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Milczarek
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Zwaka
authors.forename: Michael
authors.initials: M
authors.lastname: Kyba
authors.forename: Michelle Craig
authors.initials: MC
authors.lastname: Barton
mesh_terms: D000107:Acetylation; D000943:Antigens, Differentiation / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis; D001483:Base Sequence; D001665:Binding Sites; D002453:Cell Cycle; D002454:Cell Differentiation; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000378:metabolism / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D000090062:Kruppel-Like Factor 4; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D055550:Protein Stability; D014158:Transcription, Genetic; D014212:Tretinoin / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D000943:Antigens, Differentiation; C000715467:KLF4 protein, human; C000715468:Klf4 protein, mouse; D000090062:Kruppel-Like Factor 4; C541010:MIRN145 microRNA, human; C522425:MIRN34 microRNA, human; D035683:MicroRNAs; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D014212:Tretinoin