title: Differentiation is inhibited and a senescence pathway is activated when simian virus 40 tsA 58-transformed human retinoblasts are grown at the restrictive temperature.
abstract: Neonatal human retina cells transformed by the SV40 tumor antigens were shown to leave the cell cycle and differentiate following treatment with agents that raise intracellular levels of cyclic AMP. This was true for both precrisis and immortal cell lines. However, with time, some of the differentiated retinoblasts withdrew neurites and returned to the cell cycle. Attempts to inhibit this process by developing cell lines transformed using SV tsA 58 with a temperature-sensitive phenotype for growth did not enhance but inhibited retinoblast-differentiating capacity. Growth restriction at the nonpermissive temperature was found to activate a senescence pathway. We propose that at the nonpermissive temperature, stable SV40 T-ag-p53 complexes fragment releasing p53, which transactivates p21waf1/cip1/sdi1 with the subsequent accumulation of p21 culminating in growth inhibition and senescence.
authors.affiliation: Cancer Research Campaign Institute for Cancer Studies, Medical School, University of Birmingham, Edgbaston, United Kingdom.
authors.forename: P H
authors.initials: PH
authors.lastname: Gallimore
authors.forename: P S
authors.initials: PS
authors.lastname: Lecane
authors.forename: B
authors.initials: B
authors.lastname: Hann
authors.forename: R J
authors.initials: RJ
authors.lastname: Grand
mesh_terms: D000952:Antigens, Polyomavirus Transforming / Q000502:physiology; D017209:Apoptosis; D002453:Cell Cycle; D016923:Cell Death; D002454:Cell Differentiation; D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral / Q000502:physiology*; D016922:Cellular Senescence / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000032:analysis / Q000235:genetics; D006801:Humans; D007231:Infant, Newborn; D011518:Proto-Oncogene Proteins / Q000032:analysis; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger / Q000032:analysis; D012160:Retina / Q000166:cytology*; D013539:Simian virus 40 / Q000502:physiology*; D013696:Temperature; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051028:bcl-2-Associated X Protein
chemical_list: D000952:Antigens, Polyomavirus Transforming; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D000242:Cyclic AMP