title: Loss of the hSNF5 gene concomitantly inactivates p21CIP/WAF1 and p16INK4a activity associated with replicative senescence in A204 rhabdoid tumor cells.
abstract: hSNF5, the smallest member of the SWI/SNF chromatin remodeling complex, is lost in most malignant rhabdoid tumors (MRT). In MRT cell lines, reexpression of hSNF5 induces G1 cell cycle arrest, elevated p16INK4a, and activated replicative senescence markers, such as beta-galactosidase (beta-Gal) and plasminogen activator inhibitor-1. To compare the replicative senescence caused by hSNF5 in A204 cells to normal cellular senescence, we examined the activation of both p16INK4a and p21CIP/WAF1. Analogous to normal cellular senescence, both p16INK4a and p21CIP/WAF1 were up-regulated following hSNF5 restoration. Furthermore, we found that hSNF5 bound the p16INK4a and p21CIP/WAF1 promoters, suggesting that it directly regulates transcription of these genes. Using p16INK4a RNA interference, we showed its requirement for the replicative senescence caused by hSNF5 but not the growth arrest. Instead, p21CIP/WAF1 remained activated by hSNF5 in the absence of high p16INK4a expression, apparently causing the growth arrest in A204. Interestingly, we also found that, in the absence of p16INK4a, reexpression of hSNF5 also increased protein levels of a second cyclin-dependent kinase (CDK) inhibitor, p18INK4c. However, our data show that lack of hSNF5 does not abrogate cellular responsiveness to DNA damage or growth-inhibitory factors. In summary, our studies suggest that hSNF5 loss may influence the regulation of multiple CDK inhibitors involved in replicative senescence.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, North Carolina 27599-7295, USA.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Chai
authors.forename: Aubri L
authors.initials: AL
authors.lastname: Charboneau
authors.forename: Bryan L
authors.initials: BL
authors.lastname: Betz
authors.forename: Bernard E
authors.initials: BE
authors.lastname: Weissman
mesh_terms: D048708:Cell Growth Processes / Q000235:genetics; D045744:Cell Line, Tumor; D016922:Cellular Senescence / Q000235:genetics; D002868:Chromosomal Proteins, Non-Histone; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000172:deficiency* / Q000235:genetics*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D017353:Gene Deletion; D005786:Gene Expression Regulation; D015972:Gene Expression Regulation, Neoplastic; D019942:Genes, p16 / Q000502:physiology; D006801:Humans; D018335:Rhabdoid Tumor / Q000235:genetics* / Q000473:pathology*; D000071796:SMARCB1 Protein; D014157:Transcription Factors / Q000172:deficiency* / Q000235:genetics*; D015854:Up-Regulation
chemical_list: C493956:CDKN1A protein, human; D002868:Chromosomal Proteins, Non-Histone; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; D000071796:SMARCB1 Protein; C513266:SMARCB1 protein, human; D014157:Transcription Factors