title: tax and rex Sequences of bovine leukaemia virus from globally diverse isolates: rex amino acid sequence more variable than tax.
abstract: Bovine leukaemia virus (BLV) is an important agricultural problem with high costs to the dairy industry. Here, we examine the variation of the tax and rex genes of BLV. The tax and rex genes share 420 bases and have overlapping reading frames. The tax gene encodes a protein that functions as a transactivator of the BLV promoter, is required for viral replication, acts on cellular promoters, and is responsible for oncogenesis. The rex facilitates the export of viral mRNAs from the nucleus and regulates transcription. We have sequenced five new isolates of the tax/rex gene. We examined the five new and three previously published tax/rex DNA and predicted amino acid sequences of BLV isolates from cattle in representative regions worldwide. The highest variation among nucleic acid sequences for tax and rex was 7% and 5%, respectively; among predicted amino acid sequences for Tax and Rex, 9% and 11%, respectively. Significantly more nucleotide changes resulted in predicted amino acid changes in the rex gene than in the tax gene (P < or = 0.0006). This variability is higher than previously reported for any region of the viral genome. This research may also have implications for the development of Tax-based vaccines.
authors.affiliation: School of Public Health, Division of Infectious Diseases, University of California at Berkeley, Berkeley, CA 94720, USA. katy@uclink4.berkeley.edu
authors.forename: K M
authors.initials: KM
authors.lastname: McGirr
authors.forename: G C
authors.initials: GC
authors.lastname: Buehring
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D016384:Consensus Sequence; D016583:Enzootic Bovine Leukosis / Q000821:virology; D015967:Gene Expression Regulation, Viral; D016370:Gene Products, rex / Q000737:chemistry* / Q000235:genetics; D016356:Gene Products, tax / Q000737:chemistry* / Q000235:genetics; D005814:Genes, Viral; D016355:Genes, pX; D001909:Leukemia Virus, Bovine / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012689:Sequence Homology, Nucleic Acid; D014779:Virus Replication
chemical_list: D016370:Gene Products, rex; D016356:Gene Products, tax