title: The truncated C-terminal E2 (E2-TR) protein of bovine papillomavirus (BPV) type-1 is a transactivator that modulates transcription in vivo and in vitro in a manner distinct from the E2-TA and E8^E2 gene products.
abstract: The E2 open reading frame of bovine papillomavirus (BPV)-1 encodes a 410 amino acid (aa) transcriptional activator, E2-TA, and collinear polypeptides--E2-TR (243 aa) and E8^E2 (196 aa). E8^E2 and E2-TR share the DNA-binding domain of E2-TA, and both have been defined as transcriptional repressors. Although purified E2-TR and E8^E2 proteins specifically bound E2 sites with similar affinities, only the E2-TR stimulated transcription. Here we show that E2-TR trans-activates E2-dependent promoters 5 to 10-fold in cooperation with cellular factors and in a dose-dependent fashion in epithelial cells and fibroblasts of animal or human origin while E2-TA activated >100-fold and the E8^E2 had no effect. However, in contrast to E2-TA, E2-TR activated transcription from a promoter-proximal position. E2-TR also partially inhibited the BPV-1 P89 or heterologous promoters whereas E8^E2 led to complete repression. Thus, the BPV-1 E2-TR modulates viral gene expression in a manner distinct from other E2 proteins.
authors.affiliation: Veterans Affairs Healthcare System, Iowa City, IA 52246, USA. michael-lace@uiowa.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lace
authors.forename: Masato
authors.initials: M
authors.lastname: Ushikai
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Yamakawa
authors.forename: James R
authors.initials: JR
authors.lastname: Anson
authors.forename: Takaoki
authors.initials: T
authors.lastname: Ishiji
authors.forename: Lubomir P
authors.initials: LP
authors.lastname: Turek
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Haugen
mesh_terms: D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017384:Sequence Deletion; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C051550:E2 protein, Bovine papillomavirus; D015534:Trans-Activators; D014764:Viral Proteins