TAT and osteosarcoma: It has recently been shown that Tat-inducible lentivirus in an osteosarcoma cell line did not experience transcriptional pulsing but rather polymerase II consistently transcribed with high elongation rates of up to 50 kb/min at several different single-copy integration sites, in contrast to rates of 1 kb/min when the transgene was present in a multicopy array [33].