Multiple signaling pathways control the activation of the CEF-4/9E3 cytokine gene by pp60v-src.
The CEF-4/9E3 cytokine gene is expressed aberrantly in chicken embryo fibroblasts (CEF) transformed by the Rous sarcoma virus. The expression of CEF-4 is dependent on both transcriptional and post-transcriptional mechanisms of regulation. The characterization of the promoter region indicated that three distinct regulatory elements corresponding to an AP-1 binding site (or TRE), a PRDII/kappaB domain, and a CAAT box are involved in the activation by pp60(v-)src. In this report we investigate the signaling pathways controlling the expression of the TRE and PRDII domain. The expression of a dominant negative mutant of p21(ras) reduced the activity of both elements. In contrast a similar mutant of c-Raf-1 affected modestly the activation dependent on the TRE but not PRDII. The stress-activated protein kinase (SAPK)/Jun N-terminal kinase (JNK) pathway was important for the activity of PRDII and the TRE but was not markedly stimulated by pp60(v-)src. The addition of calphostin C and the inhibition of protein kinase C (PKC) diminished the accumulation of the CEF-4 mRNA and reduced the activity of a TRE-controlled promoter. Likewise, the depletion of PKC by chronic treatment with phorbol esters inhibited the activation of the TRE. Rous sarcoma virus-transformed CEF treated with calphostin C were also flatter, did not display a high degree of criss-crossing, and appeared morphologically normal. Hence PKC was important for the activation of AP-1 and the morphological transformation of CEF. The constitutive expression of CEF-4 was correlated with transformation only when dependent on the TRE. This was not true for PRDII, which was the only element required for the constitutive activation to the CEF-4 promoter in nontransformed cells treated chronically with phorbol esters.
Bojović
B
B
Department of Biology, York University, North York, Ontario M3J 1P3, Canada.
Rodrigues
N
N
Dehbi
M
M
Bédard
P A
PA
D000818:Animals; D030161:Avian Proteins; D001358:Avian Sarcoma Viruses; D015152:Blotting, Northern; D002472:Cell Transformation, Viral; D002642:Chick Embryo; D016207:Cytokines / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D007700:Kinetics; D009281:Naphthalenes / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D000071701:Regulatory Factor X Transcription Factors; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors
D030161:Avian Proteins; D016207:Cytokines; D004268:DNA-Binding Proteins; C071280:EMF-1 protein, Gallus gallus; C063232:HIVEP1 protein, human; D009281:Naphthalenes; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D000071701:Regulatory Factor X Transcription Factors; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D015688:Oncogene Protein pp60(v-src); D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D011493:Protein Kinase C; D016283:Proto-Oncogene Proteins p21(ras); C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate