Induction of p202, a modulator of apoptosis, during oncogenic transformation of NIH 3T3 cells by activated H-Ras (Q61L) contributes to cell survival.
Previous studies have revealed that p202 (52 kDa), an interferon (IFN) and differentiation-inducible protein, negatively regulates cell proliferation and modulates cell survival. However, the role of p202 in transformed cells remains to be investigated. Here we report that constitutive expression of oncogenic H-Ras (Q61L) in NIH 3T3 cells, which resulted in cell transformation, was associated with increases in the steady-state levels of 202 RNA and protein. Interestingly, the increase in p202 levels in transformed cells correlated with increases in the activity of the transcription factor c-Jun/AP-1, which bound to the two potential AP-1 DNA binding sites (the AP-1CS1 and AP-1CS2) in the 5'-regulatory region of the 202 gene in gel mobility shift assays. Furthermore, the site-directed mutagenesis, coupled with promoter-reporter analyses, revealed that these two AP-1 DNA binding sites contribute to the regulation of the 202 gene in Ras transformed cells. Because treatment of transformed cells with a specific inhibitor of MEK (PD 98059) resulted in significant decreases in the levels of p202, these observations raise the possibility that in transformed cells Ras/Raf/MEK pathway regulates the transcriptional activation of the 202 gene. Significantly, decreases in the levels of p202 in Ras transformed NIH 3T3 cells under reduced serum conditions increased the susceptibility to apoptosis. Collectively, our observations support the idea that the transcriptional increases in the levels of p202 by oncogenic H-Ras in NIH 3T3 cells are needed for cell survival.
Xin
Hong
H
Department of Radiation Oncology, Stritch School of Medicine, Loyola University Medical Center, 2160 South First Avenue, Building No. 1, Mail code: 114B, Maywood, IL 60153, USA.
Geng
Yanbiao
Y
Pramanik
Rocky
R
Choubey
Divaker
D
D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000378:metabolism*; D002470:Cell Survival; D002471:Cell Transformation, Neoplastic; D003593:Cytoplasm / Q000378:metabolism; D005434:Flow Cytometry; D017930:Genes, Reporter; D011905:Genes, ras; D005822:Genetic Vectors; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D016297:Mutagenesis, Site-Directed; D010750:Phosphoproteins / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014162:Transfection
D002352:Carrier Proteins; C092537:Ifi202b protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D016283:Proto-Oncogene Proteins p21(ras)