期刊
GENOMICS
卷 89, 期 4, 页码 502-511出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.ygeno.2006.12.007
关键词
bovine leukemia virus; overlapping genes; Tax; Rex; G4; R3; polymorphism; constrained evolution; selection
Bovine leukemia virus contains a pXBL region encoding the 3' parts of four regulatory proteins (Tax, Rex, G4, R3) in overlapping reading frames. Here we report the pXBL polymorphisms of 30 isolates from four countries. Rates of overall and synonymous substitutions were consistently lower, and nucleotide/amino acid composition bias and codon bias higher, in more-overlapped than in less-overlapped regions. Ratios of nonsynonymous/synonymous substitutions were lowest in the tax gene and its subregions. The 5' parts of the four genes showed selection patterns corresponding to their genomic context outside of the pXBL region. Longer G4 variants due to a natural stop codon mutation had additional triple overlap with reduced sequence variability. These data support the concept that a higher level of overlapping in coding regions correlates with greater evolutionary constraint. Tax, the most conserved among the four regulatory proteins, showed purifying selection consistent with its importance in the viral life cycle. (c) 2006 Elsevier Inc. All rights reserved.
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