title: Restoration of G1/S arrest in E1A+c-Ha-ras-transformed cells by Bcl-2 overexpression.
abstract: Here we show that introduction of human bcl-2 gene into E1A+c-Ha-ras-transformed rat embryo fibroblasts, which are highly susceptible to proapoptotic stimuli and fail to be arrested at the G(1)/S boundary following genotoxic stresses, results not only in inhibition of apoptosis, but also in restoration of the G(1)/S arrest. Overexpression of Bcl-2 did not affect proliferation rate and saturation density of E1A+c-Ha-ras transformants. Genotoxic stresses caused prolong G(1)/S arrest in Bcl-2-overexpressing transformants. Remarkably, levels and activities of Cdk2, cyclins E/A, cyclin E-Cdk2 and cyclin A-Cdk2 were unchanged during G(1)/S arrest. Introduction of Bcl-2 into E1A+c-Ha-ras-transformants resulted in accumulation of p21/Waf-1 without inhibiting cyclin-Cdk complexes. In both parental and Bcl-2-overexpressing cells, p21/Waf-1 was coimmunoprecipitated with ERK 1,2 and JNK 1,2, whereas p38 was found in complexes with p21/Waf-1 only in Bcl-2-overexpressing transformants. JNK 1,2 and p38 but not ERK 1,2 were detected in complexes with the exogenous Bcl-2. However, Bcl-2 did not affect phosphorylation of ERK 1,2, JNK 1,2 and p38. G(1)/S arrest induced by adriamycin and serum withdrawal (but not by IR) was accompanied by release of active forms of p38 from complexes with Bcl-2. We suggest that Bcl-2 restores stress-induced G(1)/S arrest without inhibiting cyclin-Cdk2 complexes and MAPK pathways.
authors.affiliation: Institute of Cytology, Russian Academy of Sciences, 194064 Tikhoretsky pr. 4, Saint-Petersburg, Russia.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Nelyudova
authors.forename: Nataliya D
authors.initials: ND
authors.lastname: Tararova
authors.forename: Nikolay D
authors.initials: ND
authors.lastname: Aksenov
authors.forename: Valery A
authors.initials: VA
authors.lastname: Pospelov
authors.forename: Tatiana V
authors.initials: TV
authors.lastname: Pospelova
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D002461:Cell Line, Transformed; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D016895:Culture Media, Serum-Free; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004247:DNA / Q000187:drug effects / Q000528:radiation effects; D004249:DNA Damage; D004317:Doxorubicin / Q000494:pharmacology; D016193:G1 Phase; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D011839:Radiation, Ionizing; D051381:Rats; D016196:S Phase; D013997:Time Factors; D014162:Transfection; D054462:p21-Activated Kinases; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000903:Antibiotics, Antineoplastic; C493958:Cdkn1a protein, rat; D016895:Culture Media, Serum-Free; D050759:Cyclin-Dependent Kinase Inhibitor p21; D019253:Proto-Oncogene Proteins c-bcl-2; D004317:Doxorubicin; D004247:DNA; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D048051:p38 Mitogen-Activated Protein Kinases