Enhancer binding factors AP-4 and AP-1 act in concert to activate SV40 late transcription in vitro.
The simian virus 40 (SV40) transcriptional enhancer is composed of multiple cis-acting DNA sequence motifs, each individually having a two- to fourfold effect on the efficiency of transcription. When various distinct cis-elements act in combination, however, a dramatic enhancement of transcription initiation often results. SV40-enhancer A-domain sequences were previously shown to be important for early and late transcription in vivo. Here we report the isolation of the enhancer binding factor AP-4, which recognizes a motif in this domain. Purified AP-4 activates SV40 late transcription in vitro, and this stimulation is augmented by the addition of transcription factor AP-1 which binds to adjacent sequences in the A-domain, suggesting coordinate action of the two factors for transcriptional enhancement. AP-1 also represses late transcription from a major in vitro start site which is poorly used in vivo, indicating that AP-1 can act as both a positive and negative regulator of SV40 late transcription. Thus by manipulating the levels of different trans-acting factors in vitro, we can recreate the pattern of SV40 late initiation observed during the viral lytic cycle in vivo.
Mermod
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Department of Biochemistry, University of California, Berkeley 94720.
Williams
T J
TJ
Tjian
R
R
D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000502:physiology*; D004742:Enhancer Elements, Genetic; D005814:Genes, Viral; D006367:HeLa Cells / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D016755:Proto-Oncogene Proteins c-jun; D013539:Simian virus 40 / Q000235:genetics*; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D016755:Proto-Oncogene Proteins c-jun; D014157:Transcription Factors; C055473:enhancer-binding protein AP-4