Involvement of E2F1 transcriptional activity in cadmium-induced cell-cycle arrest at G1 in human lung fibroblasts.
Human cadmium (Cd) exposure is associated with cancers of the lung and kidney. Using cDNA microarray analysis, we have recently reported that the expression of E2F1 is reduced by Cd in human lung fibroblasts, indicating the possibility of G1-phase arrest. To test this hypothesis, we investigated the effects of Cd on the cyclin-dependent kinase (CDK2) and retinoblastoma protein (Rb) regulatory pathways in WI38 human lung fibroblasts. We demonstrate here that G1-phase accumulation was induced by Cd in WI38 (wild-type for p53 and Rb), but not in the SV40 large T antigen-transformed variant WI38-VA13 (p53- and Rb-defective). Cd-induced cell-cycle arrest was associated with a decrease in CDK2 protein and with increase in p21 expression and p53 phosphorylation. Cd treatment caused a distinct increase in the formation of p21-cyclin E-CDK2 complex, as revealed by immunoprecipitation. The level of Rb-E2F1 complexes was increased, and the translocation of E2F1 to the nucleus was decreased by Cd treatment. Consequently, the transcriptional activity of E2F1 and the expression of the E2F1 target genes were also decreased by Cd. These results clearly demonstrate that Cd-mediated G1 arrest in WI38 cells is associated with the suppression of Rb phosphorylation and with the inhibition of E2F1 transcriptional activity.
Choi
You-Jin
YJ
College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul 151-742, Republic of Korea.
Yin
Hu-Quan
HQ
Suh
Hyo-Ryung
HR
Lee
Young-Ju
YJ
Park
So-Ra
SR
Lee
Byung-Hoon
BH
D002104:Cadmium / Q000633:toxicity*; D002460:Cell Line; D051357:Cyclin-Dependent Kinase 2 / Q000032:analysis / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000032:analysis / Q000378:metabolism; D050687:E2F1 Transcription Factor / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects; D016193:G1 Phase / Q000187:drug effects*; D006801:Humans; D008168:Lung / Q000187:drug effects*; D010766:Phosphorylation; D016160:Retinoblastoma Protein / Q000032:analysis / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*; D016159:Tumor Suppressor Protein p53 / Q000032:analysis / Q000378:metabolism
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D002104:Cadmium; D051357:Cyclin-Dependent Kinase 2