Pleiotropic effect of the human T-cell leukemia virus Tax protein on the DNA binding activity of eukaryotic transcription factors.
The Tax protein, encoded by the human T-cell leukemia virus type I, is a potent activator of viral and cellular gene transcription. Tax does not bind DNA directly but appears to trans-activate through an interaction with host-cell transcription factors that recognize sequences within the promoters of Tax-responsive genes. Cellular transcriptional activators implicated in mediating Tax trans-activation include members of the activating transcription factor/cAMP response element binding protein (ATF/CREB) family of proteins, serum response factor, Fos-Jun, and NF-kappa B. Recent evidence suggests that Tax may stimulate human T-cell leukemia virus type I transcription, at least in part, through enhanced binding of ATF/CREB proteins to their recognition elements within the Tax-responsive 21-bp repeats of the viral promoter. In this report, we demonstrate that Tax also enhances the site-specific DNA binding activity of serum response factor and Fos-Jun and modestly enhances the binding of the NF-kappa B subunits, p50 and p65. We also show that Tax increases the DNA binding activity of the eukaryotic transcription factors ATF-1, Sp1, and GAL4. These results are consistent with the finding that Tax is highly pleiotropic and suggest that Tax trans-activation may involve enhancement in the DNA binding activity of target transcriptional regulatory proteins. In addition, we show that the mechanism of Tax-enhanced DNA binding activity does not involve an alteration in the redox state of the target protein.
Armstrong
A P
AP
Department of Biochemistry, Colorado State University, Fort Collins 80523.
Franklin
A A
AA
Uittenbogaard
M N
MN
Giebler
H A
HA
Nyborg
J K
JK
D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D016356:Gene Products, tax / Q000502:physiology*; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D010084:Oxidation-Reduction; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D026362:Serum Response Factor; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D016356:Gene Products, tax; D016328:NF-kappa B; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D011994:Recombinant Proteins; D026362:Serum Response Factor; D014157:Transcription Factors