Derivation and functional characterization of a consensus DNA binding sequence for the tas transcriptional activator of simian foamy virus type 1.
Although DNA binding sites specific for the Bel-1 and Tas transcriptional activators, encoded, respectively, by the human and simian foamy viruses, have been mutationally defined, they show little evident sequence identity. As a result, the sequence determinants for DNA binding by both Bel-1 and Tas have remained unclear. Here, we report the use of a novel in vivo randomization and selection strategy to identify a Tas DNA binding site consensus. This approach takes advantage of the fact that Tas can effectively activate gene expression in yeast cells via a Tas DNA binding site derived from the simian foamy virus type 1 (SFV-1) internal promoter. The defined Tas DNA binding site consensus extends over approximately 25 bp and contains a critical core sequence of approximately 5 bp. Positions adjacent to this core sequence, while clearly also subject to selection, show a significantly higher level of sequence variation. Surprisingly, the wild-type SFV-1 internal promoter Tas DNA binding site fails to conform to the consensus at several positions. Further analysis demonstrated that the consensus sequence bound Tas more effectively than did the wild-type sequence in vitro and could mediate an enhanced Tas response in vivo when substituted into the SFV-1 internal promoter context. These findings explain the limited sequence identity observed for mutationally defined Tas or Bel-1 response elements and should facilitate the identification of Tas DNA target sites located elsewhere in the SFV-1 genome.
Kang
Y
Y
Department of Genetics, Duke University Medical Center, Durham, North Carolina 27710, USA.
Cullen
B R
BR
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D012191:Retroviridae Proteins / Q000378:metabolism*; D016092:Spumavirus / Q000235:genetics*; D015534:Trans-Activators / Q000378:metabolism*
D004268:DNA-Binding Proteins; D012191:Retroviridae Proteins; D015534:Trans-Activators; C074061:bel1 protein, Human foamy virus; D004247:DNA