Mapping of polyomavirus middle T domain that is responsible for AP-1 activation.
Cell transformation by Polyomavirus middle T (MT) oncoprotein involves binding and activation of several cytoplasmic proteins that participate in growth factors-induced mitogenic signal transduction to the nucleus. We have previously reported that the AP-1 transcriptional complex is a target for MT during cell transformation. To analyse the interactions between MT and cellular proteins that are required for constitutive AP-1 activation, we compared wild type and transformation-defective MT mutant cell lines. High AP-1 activity, assessed by gel mobility shift assays, displayed by MT-overexpressing cells, is dependent on MT binding to phosphatidylinositol-3 kinase (P13K). Treatment with wortmannin (a specific P13K inhibitor) leads to decreased AP-1 activity. Supershift and Western blot analysis with specific antisera, indicate that JunB and cJun, but not cFos or FosB are present in the AP-1 complex. The results confirm the AP-1 complex as a downstream MT target and indicate that AP-1 activation may not be sufficient for cell transformation, since two transformation-defective MT mutants (250phe and MT322) display high AP-1 activity.
Oliveira
M L
ML
Instituto de Química, Universidade de São Paulo, SP, Brasil.
Roberts
T M
TM
Druker
B J
BJ
Armelin
M C
MC
D016475:3T3 Cells; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002472:Cell Transformation, Viral; D002874:Chromosome Mapping; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D051379:Mice; D016296:Mutagenesis; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D000077191:Wortmannin
D000730:Androstadienes; D000952:Antigens, Polyomavirus Transforming; D004791:Enzyme Inhibitors; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D019869:Phosphatidylinositol 3-Kinases; D000077191:Wortmannin