title: Bovine leukemia virus transcription is controlled by a virus-encoded trans-acting factor and by cis-acting response elements.
abstract: Bovine leukemia virus (BLV) gene expression is exquisitely regulated at multiple levels, including a transcriptional control effected by virus-encoded trans-acting factors and cis-acting target sequences. Like the human T-cell leukemia viruses type I and type II, but unlike other RNA tumor viruses, BLV contains several open reading frames at the 3' end of its genome. A subgenomic mRNA which encodes two overlapping reading frames from this region could produce proteins of 38 and 18 kilodaltons (kDa). A series of cis-trans experiments using transfected virus gene constructs in different combinations revealed that expression of the 38-kDa protein was both necessary and sufficient to activate, in trans, the BLV promoter. This activation was specific for the BLV long terminal repeat, as a variety of related retroviral promoters were not responsive to the expression of the 38-kDa protein p38(XBL). Deletion analysis and construction of chimeric promoters identified a 75-base-pair long terminal repeat region which functions like a p38(XBL)-dependent enhancer element.
mesh_terms: D003001:Cloning, Molecular; D017977:Deltaretrovirus / Q000235:genetics; D005786:Gene Expression Regulation; D005814:Genes, Viral; D001909:Leukemia Virus, Bovine / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D012190:Retroviridae / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics*
chemical_list: D014157:Transcription Factors; D014764:Viral Proteins