Expression and characterization of the trans-activating protein Tax of human T-cell leukemia virus type I in Saccharomyces cerevisiae.
The trans-activator protein Tax of human T-cell leukemia virus type I (HTLV-I) stimulates transcription of the viral genome from the long terminal repeat. With a reporter HIS4TATA::lacZ fusion gene, the transcriptional activity of the Tax-responsive element in the long terminal repeat was tested in Saccharomyces cerevisiae. We found that fragments containing the 21-bp repeat of the HTLV-I enhancer stimulate synthesis of beta-galactosidase activity 15- to 20-fold. To test the ability of the Tax protein to trans activate the HTLV-I enhancer in yeast cells, the pX region of HTLV-I, encoding the Tax protein, was cloned under the control of the yeast GAL1 promoter. The expressed Tax protein is localized in the nucleus and associated with the yeast nuclear matrix fraction. In yeast cells that contained the integrated tax gene, two- to sixfold stimulation of expression from the HTLV-I enhancer was detected at the early stages of tax induction. This in vivo reconstitution system provides a new approach for examining the host factor(s), the signal transduction mechanism(s), and the role of nuclear architecture involved in Tax-mediated trans activation.
Wu
L C
LC
Public Health and Environmental Laboratories, New Jersey State Department of Health, Trenton 08625-0360.
Tan
T H
TH
Shahied
S I
SI
D015153:Blotting, Western; D003001:Cloning, Molecular / Q000379:methods; D004742:Enhancer Elements, Genetic; D016356:Gene Products, tax / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D015368:Human T-lymphotropic virus 1 / Q000235:genetics* / Q000378:metabolism; D015530:Nuclear Matrix / Q000378:metabolism; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
D016356:Gene Products, tax; D011994:Recombinant Proteins; D001616:beta-Galactosidase