title: Important role of N108 residue in binding of bovine foamy virus transactivator Tas to viral promoters.
abstract: Bovine foamy virus (BFV) encodes the transactivator BTas, which enhances viral gene transcription by binding to the long terminal repeat promoter and the internal promoter. In this study, we investigated the different replication capacities of two similar BFV full-length DNA clones, pBS-BFV-Y and pBS-BFV-B.
  
  
  
  Here, functional analysis of several chimeric clones revealed a major role for the C-terminal region of the viral genome in causing this difference. Furthermore, BTas-B, which is located in this C-terminal region, exhibited a 20-fold higher transactivation activity than BTas-Y. Sequence alignment showed that these two sequences differ only at amino acid 108, with BTas-B containing N108 and BTas-Y containing D108 at this position. Results of mutagenesis studies demonstrated that residue N108 is important for BTas binding to viral promoters. In addition, the N108D mutation in pBS-BFV-B reduced the viral replication capacity by about 1.5-fold.
  
  
  
  Our results suggest that residue N108 is important for BTas binding to BFV promoters and has a major role in BFV replication. These findings not only advances our understanding of the transactivation mechanism of BTas, but they also highlight the importance of certain sequence polymorphisms in modulating the replication capacity of isolated BFV clones.
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China.
authors.forename: Tiejun
authors.initials: T
authors.lastname: Bing
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China.
authors.forename: Suzhen
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Liu
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China.
authors.forename: Zhibin
authors.initials: Z
authors.lastname: Liang
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Shao
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China.
authors.forename: Song
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China.
authors.forename: Wentao
authors.initials: W
authors.lastname: Qiao
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China. juantan@nankai.edu.cn.
authors.forename: Juan
authors.initials: J
authors.lastname: Tan
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000821:virology*; D015967:Gene Expression Regulation, Viral; D011401:Promoter Regions, Genetic; D012192:Retroviridae Infections / Q000662:veterinary* / Q000821:virology; D016092:Spumavirus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D015534:Trans-Activators; D014764:Viral Proteins
keywords: BTas; Bovine foamy virus; Infectious clone; Promoter