title: [Rat embryo fibroblasts transformed by complementation with oncogenes E1A+E1B-19 and E1A+cHa-ras differ in the ability to realize the G1/S block in serum free media].
abstract: The capability of REF cells transformed by EA + E1B-19 kDa and EA + cHa-ras oncogenes to realize the G1/S cell cycle arrest upon serum starvation was studied. The amount of cyclin-kinase inhibitor protein p27/Kip was shown to increase in both normal and transformed cells. However, the p27/Kip-bound cyclin-kinase complexes of transformed cells were found to be active, implying the functional inactivation of p27/Kip inhibitor. Nevertheless, in contrast to E1A + cHa-ras transformants, E1A + E1B-19 kDa transformants undergo the G1 cell cycle arrest. The G1 cell cycle block correlates with the decrease in cyclinE-Cdk2 activity. Since cyclinE-Cdk2 complexes need Thr-160 phosphorylation of Cdk2 by CAK-kinase for full activity, we have analysed the Cdk-7 associated activity upon serum starvation using gst-Cdk2 as a substrate. Serum starvation did not affect CAK activity either in E1A + cHa-ras or in E1A + E1B-19 kDa transformants. Thus, selective suppression of cyclineE-Cdk2 activity in E1A + E1B-19 kDa transformants upon serum starvation does not arise from the action of cyclin-kinase inhibitors, or from change in CAK activity.
authors.affiliation: Institute of Cytology RAS, St. Petersburg.
authors.forename: A I
authors.initials: AI
authors.lastname: Brichkina
authors.forename: N D
authors.initials: ND
authors.lastname: Tararova
authors.forename: N D
authors.initials: ND
authors.lastname: Aksenov
authors.forename: V A
authors.initials: VA
authors.lastname: Pospelov
authors.forename: T V
authors.initials: TV
authors.lastname: Pospelova
mesh_terms: D017500:Adenovirus E1A Proteins / Q000235:genetics*; D017501:Adenovirus E1B Proteins / Q000235:genetics*; D000818:Animals; D002453:Cell Cycle / Q000235:genetics*; D018797:Cell Cycle Proteins / Q000502:physiology; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic; D002472:Cell Transformation, Viral; D016895:Culture Media, Serum-Free; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000502:physiology; D004622:Embryo, Mammalian / Q000166:cytology; D005347:Fibroblasts / Q000473:pathology* / Q000502:physiology; D016193:G1 Phase / Q000235:genetics; D011905:Genes, ras / Q000235:genetics*; D051381:Rats; D016196:S Phase / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics*; D025521:Tumor Suppressor Proteins / Q000502:physiology
chemical_list: D017500:Adenovirus E1A Proteins; D017501:Adenovirus E1B Proteins; C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D016895:Culture Media, Serum-Free; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases