title: G1/S arrest induced by histone deacetylase inhibitor sodium butyrate in E1A + Ras-transformed cells is mediated through down-regulation of E2F activity and stabilization of beta-catenin.
abstract: Tumor cells are often characterized by a high and growth factor-independent proliferation rate. We have previously shown that REF cells transformed with oncogenes E1A and c-Ha-Ras do not undergo G(1)/S arrest of the cell cycle after treatment with genotoxic factors. In this work, we used sodium butyrate, a histone deacetylase inhibitor, to show that E1A + Ras transformants were able to stop proliferation and undergo G(1)/S arrest. Apart from inducing G(1)/S arrest, sodium butyrate was shown to change expression of a number of cell cycle regulatory genes. It down-regulated cyclins D1, E, and A as well as c-myc and cdc25A and up-regulated the cyclin-kinase inhibitor p21(waf1). Accordingly, activities of cyclin E-Cdk2 and cyclin A-Cdk2 complexes in sodium butyrate-treated cells were decreased substantially. Strikingly, E2F1 expression was also down-modulated at the levels of gene transcription, the protein content, and the E2F transactivating capability. To further study the role of p21(waf1) in the sodium butyrate-induced G(1)/S arrest and the E2F1 down-modulation, we established E1A + Ras transformants from mouse embryo fibroblast cells with deletion of the cdkn1a (p21(waf1)) gene. Despite the absence of p21(waf1), sodium butyrate-treated mERas transformants reveal a slightly delayed G(1)/S arrest as well as down-modulation of E2F1 activity, implying that the observed effects are mediated through an alternative p21(waf1)-independent signaling pathway. Subsequent analysis showed that sodium butyrate induced accumulation of beta-catenin, a downstream component of the Wnt signaling. The results obtained indicate that the antiproliferative effect of histone deacetylase inhibitors on E1A + Ras-transformed cells can be mediated, alongside other mechanisms, through down-regulation of E2F activity and stabilization of beta-catenin.
authors.affiliation: Institute of Cytology, Russian Academy of Sciences, St. Petersburg 194064, Russia.
authors.forename: Maria V
authors.initials: MV
authors.lastname: Abramova
authors.affiliation: Institute of Cytology, Russian Academy of Sciences, St. Petersburg 194064, Russia.
authors.forename: Tatiana V
authors.initials: TV
authors.lastname: Pospelova
authors.affiliation: Institute of Cytology, Russian Academy of Sciences, St. Petersburg 194064, Russia.
authors.forename: Fedor P
authors.initials: FP
authors.lastname: Nikulenkov
authors.affiliation: Gene Response Unit, NCI, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Hollander
authors.affiliation: Gene Response Unit, NCI, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Fornace
authors.affiliation: Institute of Cytology, Russian Academy of Sciences, St. Petersburg 194064, Russia. Electronic address: Pospelov_v@mail.ru.
authors.forename: Valery A
authors.initials: VA
authors.lastname: Pospelov
mesh_terms: D017500:Adenovirus E1A Proteins / Q000378:metabolism*; D000818:Animals; D002087:Butyrates / Q000494:pharmacology*; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D050687:E2F1 Transcription Factor / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016193:G1 Phase; D006801:Humans; D058610:Isobutyrates; D051379:Mice; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D051381:Rats; D016196:S Phase; D051176:beta Catenin / Q000378:metabolism*; D020687:cdc25 Phosphatases / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D017500:Adenovirus E1A Proteins; D002087:Butyrates; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050687:E2F1 Transcription Factor; D004791:Enzyme Inhibitors; D058610:Isobutyrates; D016271:Proto-Oncogene Proteins c-myc; D051176:beta Catenin; C020380:isobutyric acid; C517004:CDC25A protein, human; C517005:Cdc25a protein, mouse; C517007:Cdc25a protein, rat; D020687:cdc25 Phosphatases; D018631:ras Proteins