An adenovirus E4 gene product trans-activates E2 transcription and stimulates stable E2F binding through a direct association with E2F.
The adenovirus E4 gene encodes a trans-activating function that can stimulate the E2 promoter. E2 promoter sequences required for E4 trans-activation are identical to those required for E1A trans-activation, and these principally are the E2 promoter binding factor (E2F) binding sites. Furthermore, full activation of E2F DNA binding activity requires both E1A and E4 action. Analysis of a series of mutant E4 viruses identifies open reading frame (orf) 6/7 of the E4 transcription unit as that required for activation of E2F binding activity. In addition, the assay of various E4 cDNAs demonstrates that the E4 orf 6/7 also is responsible for the trans-activation of E2 transcription. Translation of the E4 orf 6/7 mRNA, but not a control mRNA, in a reticulocyte extract generates an activity that can stimulate cooperative binding of E2F in vitro, consistent with recent in vivo assays that demonstrate a role for the E4 gene in E2F stable complex formation. This stimulation is due to a direct interaction of the E4 protein with E2F since an antibody that recognizes the E4 orf 6/7 polypeptide detects this E4 protein in the E2F-DNA complex. We conclude that the E4 orf 6/7 product interacts with the E2F factor altering binding to allow formation of a stable complex that results in a stimulation of transcription.
Neill
S D
SD
Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710.
Hemstrom
C
C
Virtanen
A
A
Nevins
J R
JR
D017456:Adenovirus Early Proteins; D000260:Adenoviruses, Human / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005814:Genes, Viral; D006367:HeLa Cells; D006801:Humans; D009856:Oncogene Proteins, Viral / Q000378:metabolism*; D010957:Plasmids; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014709:Vero Cells; D015678:Viral Structural Proteins / Q000235:genetics*
D017456:Adenovirus Early Proteins; D004268:DNA-Binding Proteins; D009856:Oncogene Proteins, Viral; D015534:Trans-Activators; D015678:Viral Structural Proteins