Sequence-specific and general transcriptional activation by the bovine papillomavirus-1 E2 trans-activator require an N-terminal amphipathic helix-containing E2 domain.
The sequence-specific trans-activator protein of bovine papillomavirus (BPV)-1, E2, strongly increases transcription at promoters containing papillomaviral ACCG(N)4CGGT (E2P) cis motifs, but can also activate a wide range of co-transfected promoters without E2P cores to a lower extent. Analysis of multiple E2 mutants in transfected cells revealed that the C-terminal DNA binding E2 domain binds to the E2P cis sequences in the form of pre-existing nuclear dimers. The DNA binding function of E2 was required for specific trans-activation of the E2P elements, as well as for the function of the previously described C-terminal 'short E2' transrepressor. In addition to the C terminus, specific trans-activation also required an intact N-terminal half of the E2 protein. When expressed alone, the N-terminal E2 domain was found to activate heterologous promoters without E2P elements to an extent comparable to wild-type E2, and therefore represents the functional transcription activation domain of the E2 factor. In contrast to other DNA-binding activator proteins described to date, the transcriptional activation by the E2 factor can occur without specific DNA binding. Its mechanism may thus involve protein--protein interactions between common transcription factors and the N-terminal E2 domain which contains amphipathic helix motifs.
Haugen
T H
TH
Department of Pathology, VAMC, Iowa City, IA.
Turek
L P
LP
Mercurio
F M
FM
Cripe
T P
TP
Olson
B J
BJ
Anderson
R D
RD
Seidl
D
D
Karin
M
M
Schiller
J
J
D000818:Animals; D001483:Base Sequence; D052688:Bovine papillomavirus 1 / Q000235:genetics* / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D015696:Gene Products, tat; D005814:Genes, Viral; D009154:Mutation; D027383:Papillomaviridae / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D014162:Transfection; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism
D004279:DNA, Viral; D004268:DNA-Binding Proteins; C051550:E2 protein, Bovine papillomavirus; D015696:Gene Products, tat; D012097:Repressor Proteins; D014157:Transcription Factors; D014764:Viral Proteins