title: Cyclin D2 and the CDK substrate p220(NPAT) are required for self-renewal of human embryonic stem cells.
abstract: Self-renewal of pluripotent human embryonic stem (hES) cells utilizes an abbreviated cell cycle that bypasses E2F/pRB-dependent growth control. We investigated whether self-renewal is alternatively regulated by cyclin/CDK phosphorylation of the p220(NPAT)/HiNF-P complex to activate histone gene expression at the G1/S phase transition. We show that cyclin D2 is prominently expressed in pluripotent hES cells, but cyclin D1 eclipses cyclin D2 during differentiation. Depletion of cyclin D2 or p220(NPAT) causes a cell cycle defect in G1 reflected by diminished phosphorylation of p220(NPAT), decreased cell cycle dependent histone H4 expression and reduced S phase progression. Thus, cyclin D2 and p220(NPAT) are principal cell cycle regulators that determine competency for self-renewal in pluripotent hES cells. While pRB/E2F checkpoint control is relinquished in human ES cells, fidelity of physiological regulation is secured by cyclin D2 dependent activation of the p220(NPAT)/HiNF-P mechanism that may explain perpetual proliferation of hES cells without transformation or tumorigenesis.
authors.affiliation: Department of Cell Biology and Cancer Center, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
authors.forename: Klaus A
authors.initials: KA
authors.lastname: Becker
authors.forename: Prachi N
authors.initials: PN
authors.lastname: Ghule
authors.forename: Jane B
authors.initials: JB
authors.lastname: Lian
authors.forename: Janet L
authors.initials: JL
authors.lastname: Stein
authors.forename: Andre J
authors.initials: AJ
authors.lastname: van Wijnen
authors.forename: Gary S
authors.initials: GS
authors.lastname: Stein
mesh_terms: D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D019938:Cyclin D1 / Q000378:metabolism; D056742:Cyclin D2 / Q000235:genetics / Q000378:metabolism*; D051358:Cyclin-Dependent Kinase 4 / Q000235:genetics / Q000378:metabolism*; D053595:Embryonic Stem Cells / Q000201:enzymology*; D006657:Histones / Q000378:metabolism; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D039904:Pluripotent Stem Cells / Q000201:enzymology*; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D013997:Time Factors
chemical_list: C530104:CCND1 protein, human; C080336:CCND2 protein, human; D018797:Cell Cycle Proteins; D056742:Cyclin D2; C442219:HINFP protein, human; D006657:Histones; C101693:NPAT protein, human; D009687:Nuclear Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D019938:Cyclin D1; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4