TAT and infection: 3A, upper panel). A 90% decrease in HuR levels was observed. Cells were fixed 24 hours after infection, and stained with X-Gal, as previously described [19]. An aliquot of cells was collected, lysed and analyzed by western blotting. HuR knockdown was maintained throughout the experiment, as 90% silencing of HuR was still observed at the time of fixation (fig. 3A, lower panel). Tat-activated LTR was used for β-galactosidase production and the counting of successfully infected cells (fig. 3B).