Indirect binding of human T-cell leukemia virus type I tax1 to a responsive element in the viral long terminal repeat.
Several laboratories have demonstrated that tandem copies of the human T-cell leukemia virus type I 21-base-pair (bp) repeat cloned upstream of either a homologous or heterologous promoter increase transcription in the presence of tax1 protein. In this report, we provide evidence for a second tax1-responsive sequence in the viral long terminal repeat. Analysis of human T-cell leukemia virus type I promoter deletion mutants and plasmids containing cloned oligonucleotide motifs demonstrated that this 47-bp sequence, located between -117 and -163, confers responsiveness to tax1. We further demonstrated that proteins present in HeLa nuclear extracts bind specifically to this tax1-responsive sequence. Mutants that affected in vivo activity also decreased in vitro binding. Using an in vitro binding assay, we demonstrated that tax1 interacts indirectly with the 47-bp sequence, most likely through protein-protein interaction. Thus, while tax1 does not bind directly to DNA to enhance transcription, it may influence sequence-specific responses by interacting with the primary DNA-protein complex.
Marriott
S J
SJ
Laboratory of Molecular Virology, National Cancer Institute, Bethesda, Maryland 20892.
Boros
I
I
Duvall
J F
JF
Brady
J N
JN
D000818:Animals; D015500:Chloramphenicol O-Acetyltransferase; D004252:DNA Mutational Analysis; D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000378:metabolism*; D006367:HeLa Cells; D015368:Human T-lymphotropic virus 1 / Q000235:genetics*; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D010957:Plasmids; D012045:Regulatory Sequences, Nucleic Acid; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection
D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D015696:Gene Products, tat; D009687:Nuclear Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D015500:Chloramphenicol O-Acetyltransferase