title: p21(CIP1) Controls proliferating cell nuclear antigen level in adult cardiomyocytes.
abstract: Cell cycle withdrawal associated with terminal differentiation is responsible for the incapability of many organs to regenerate after injury. Here, we employed a cell-free system to analyze the molecular mechanisms underlying cell cycle arrest in cardiomyocytes. In this assay, incubation of S phase nuclei mixed with cytoplasmic extract of S phase cells and adult primary cardiomyocytes results in a dramatic reduction of proliferating cell nuclear antigen (PCNA) protein levels. This effect was blocked by the proteasome inhibitors MG132 and lactacystin, whereas actinomycin D and cycloheximide had no effect. Immunodepletion and addback experiments revealed that the effect of cardiomyocyte extract on PCNA protein levels is maintained by p21 but not p27. In serum-stimulated cardiomyocytes PCNA expression was reconstituted, whereas the protein level of p21 but not that of p27 was reduced. Cytoplasmic extract of serum-stimulated cardiomyocytes did not influence the PCNA protein level in S phase nuclei. Moreover, the hypertrophic effect of serum stimulation was blocked by ectopic expression of p21 and the PCNA protein level was found to be upregulated in adult cardiomyocytes derived from p21 knockout mice. Our data provide evidence that p21 regulates the PCNA protein level in adult cardiomyocytes, which has implications for cardiomyocyte growth control.
authors.affiliation: Department of Cardiology, Campus Virchow Clinic, Charité, Humboldt University, Max Delbrück Center for Molecular Medicine, Berlin, Germany.
authors.forename: Felix B
authors.initials: FB
authors.lastname: Engel
authors.forename: Ludger
authors.initials: L
authors.lastname: Hauck
authors.forename: Manfred
authors.initials: M
authors.lastname: Boehm
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Nabel
authors.forename: Rainer
authors.initials: R
authors.lastname: Dietz
authors.forename: Rüdiger
authors.initials: R
authors.lastname: von Harsdorf
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D002454:Cell Differentiation; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D002474:Cell-Free System; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism / Q000502:physiology*; D003513:Cycloheximide / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D019084:Fluorescent Antibody Technique, Indirect; D015151:Immunoblotting; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008840:Microfilament Proteins / Q000378:metabolism; D009124:Muscle Proteins; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D018809:Proliferating Cell Nuclear Antigen / Q000096:biosynthesis*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D016196:S Phase; D015854:Up-Regulation
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D008840:Microfilament Proteins; D009124:Muscle Proteins; D018809:Proliferating Cell Nuclear Antigen; D011500:Protein Synthesis Inhibitors; C058992:Tagln protein, mouse; D003609:Dactinomycin; D003513:Cycloheximide