FIG. 1.

Expression of HTLV-1 Tax causes growth arrest and loss of cell viability in S. cerevisiae. (A) W303-1a cells transformed with the Gal10-Tax (WT-Tax) or Gal10-ΔTax (ΔTax) plasmid were streaked on agar plates containing 2% raffinose (Raf) or 2% raffinose plus 2% galactose (Raf+Gal). Gal10-ΔTax is the same as Gal10-Tax except that the Tax reading frame was disrupted by filling in the NcoI site that overlaps the ATG translational start site. (B) Immunoblot (WB) analysis of HTLV-1 tax expression in S. cerevisiae. W303-1a/Gal10-Tax and W303-1a/Gal10-ΔTax were induced with galactose as described in Materials and Methods. Cell lysates were prepared, resolved on SDS-12% PAGE, transferred to a nitrocellulose membrane, and probed with a mouse monoclonal antibody against Tax. (C) W303-1a (solid circles) and W303-1a/Gal10-Tax (solid triangles) cells were grown in SC medium containing 2% raffinose and transferred to SC medium containing 2% raffinose with or without 2% galactose at time zero. Aliquots of cells were collected at different time points, and light absorbance at 600 nm was measured with a spectrophotometer. (D) The cell number in each aliquot was determined microscopically with a hemacytometer. (E) At different times after galactose induction, 500 cells each from W303-1a and W303-1a/Gal10-Tax were plated on YPAD plates for 2 days. Colony numbers were counted and normalized against the number of cells plated. Percent cell viability was plotted as a function of time after induction of Tax expression.