The cell cycle effect of human T-lymphotropic virus type 1 (HTLV-1) trans-activator, Tax, in live cells. A reporter cell line, HeLa/18x21-EGFP, that produces the green fluorescence protein upon Tax expression was transduced with Ad-Tax at an MOI of 20 for 24 hours. The cells were then monitored using time-lapse microscopy over the course of 138 hours. The un-transduced HeLa cell (colorless) in the visual field continued to proliferate and formed a sizable colony. The Ad-Tax-transduced cell (in green), however, became enlarged, showed significant cell movement, but failed to undergo cell division, and assumed a senescence phenotype.