HIV-1 IN-induced lethal phenotype in HP16 yeast strain is independent of its catalytic activity.A. The effect of IN expression on yeast growth by the “drop test”. Equal amounts of different p424Gal1-IN transformed yeast cells were serially diluted and spotted onto either non-inducible agar plates (left panel) or inducible agar plates (right panel). After 3 to 5 days, yeast growth was recorded photographically. B. The effect of HIV-1 IN on yeast growth in liquid culture. Transformed yeast cells were grown in non-inducible media (upper panel) or in inducible media (lower panel) at 30°C for 24 h. Yeast growth was monitored by the measurement of yeast culture density by spectrophotometric analysis at a wavelength of 600 nm (A600). C. IN-mediated yeast growth arrest in a galactose dose-dependent manner. Equal amounts of p424-Gal-IN- and p424-Gal-IN-DD64/116E/A-transformed yeast cells were cultured in different concentrations of galactose for 2 days and the yeast growth was then monitored by spectrophotometric assay. D. IN expression levels were detected in yeast cells in inducible media containing different concentrations of galactose for 6 hrs. Then, cells were lysed and subjected to IP with anti-HIV serum followed by WB with anti-IN antibody.