3-Methylcholanthrene, an AhR agonist, caused cell-cycle arrest by histone deacetylation through a RhoA-dependent recruitment of HDAC1 and pRb2 to E2F1 complex

• Published in: PloS one 2014-03, Vol.9 (3), p.e92793-e92793
• Main Authors: Chang, Chih-Cheng, Sue, Yuh-Mou, Yang, Nian-Jie, Lee, Yi-Hsuan, Juan, Shu-Hui
• Format: Article
• Language: English
• Subjects: 1-Phosphatidylinositol 3-kinase; 3-Methylcholanthrene; Acetylation - drug effects; Activation; Animals; Aromatic compounds; Biology and Life Sciences; Cancer; Cell adhesion & migration; Cell cycle; Cell Cycle Checkpoints - drug effects; Cell Cycle Proteins - metabolism; Cell proliferation; Cyclin D3; Cyclin-dependent kinase 2; Cyclin-dependent kinase inhibitor p27; Cyclin-dependent kinases; Deacetylation; Deactivation; Deoxyribonucleic acid; Dioxins; DNA; DNA biosynthesis; DNA synthesis; E2F1 Transcription Factor - metabolism; Electrophoretic mobility; Endothelial cells; Endothelial Cells - drug effects; Endothelial Cells - metabolism; Epigenetic inheritance; Epigenetics; G1 phase; Gene expression; Gene Expression Regulation; Genes; Histone deacetylase; Histone Deacetylase 1 - metabolism; Histones - metabolism; Homology; Hydroxymethylglutaryl-CoA Reductase Inhibitors - pharmacology; Immunoprecipitation; Inactivation; Intracellular Space - metabolism; Kinases; Ligands; Male; Medicine; Methylcholanthrene - pharmacology; Mice; Molecular modelling; Multiprotein Complexes - metabolism; Nuclear transport; PCB; Phase transitions; Phosphatases; Phosphatidylinositol 3-Kinases; Phosphorylation; Physiology; Polychlorinated biphenyls; Polycyclic aromatic hydrocarbons; Protein Binding; Protein Transport; Proteins; Proto-Oncogene Proteins c-raf - metabolism; Proto-Oncogene Proteins p21(ras) - metabolism; PTEN Phosphohydrolase - metabolism; PTEN protein; Receptors, Aryl Hydrocarbon - agonists; Recruitment; Regulatory proteins; Retina; Retinoblastoma; Retinoblastoma-Like Protein p130 - metabolism; rhoA GTP-Binding Protein - metabolism; RhoA protein; Signal Transduction - drug effects; Simvastatin; Smooth muscle; Statins; Tensin; Transcription factors; Translocation
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0092793

We previously showed that treating vascular endothelial cells with 3-methylcholanthrene (3MC) caused cell-cycle arrest in the Go/G1 phase; this resulted from the induction of p21 and p27 and a decreased level and activity of the cyclin-dependent kinase, Cdk2. We further investigated the molecular mechanisms that modulate cell-cycle regulatory proteins through the aryl-hydrocarbon receptor (AhR)/Ras homolog gene family, member A (RhoA) dependent epigenetic modification of histone. AhR/RhoA activation mediated by 3MC was essential for the upregulation of retinoblastoma 2 (pRb2) and histone deacetylase 1 (HDAC1), whereas their nuclear translocation was primarily modulated by RhoA activation. The combination of increased phosphatase and tensin homolog (PTEN) activity and decreased phosphatidylinositide 3-kinase (PI3K) activation by 3MC led to the inactivation of the Ras-cRaf pathway, which contributed to pRb2 hypophosphorylation. Increased HDAC1/pRb2 recruitment to the E2F1 complex decreased E2F1-transactivational activity and H3/H4 deacetylation, resulting in the downregulation of cell-cycle regulatory proteins (Cdk2/4 and Cyclin D3/E). Co-immunoprecipitation and electrophoretic mobility shift assay (EMSA) results showed that simvastatin prevented the 3MC-increased binding activities of E2F1 proteins in their promoter regions. Additionally, RhoA inhibitors (statins) reversed the effect of 3MC in inhibiting DNA synthesis by decreasing the nuclear translocation of pRb2/HDAC1, leading to a recovery of the levels of cell-cycle regulatory proteins. In summary, 3MC decreased cell proliferation by the epigenetic modification of histone through an AhR/RhoA-dependent mechanism that can be rescued by statins.