TAL1 knockdown by shRNA affects growth and gene expression in Jurkat cells. (A) Stable expression of a shRNA against TAL1 in Jurkat cells led to decreased TAL1 protein levels, as measured by Western blotting using a monoclonal antibody against TAL1. The first 2 lanes show results for 2 different clones expressing control shRNAs (Control RNAi), compared with the results of 3 separate clones expressing the TAL1-specfic shRNA in lanes 3-5 (TAL1 RNAi). The membrane was stripped and reprobed with an antibody against α-tubulin to verify equal loading. (B) Quantitative RT-PCR using RNA prepared from the same Jurkat-cell clones shown in panel A that stably express a control shRNA (▧) or the TAL1 shRNA (▪) reveals 70% to 90% knockdown of TAL1 at the RNA level in TAL1 knockdown cells. Error bars indicate standard deviations. (C) TAL1 knockdown affects the growth rate of Jurkat cells. Cells (5 × 10⁴) from clones stably expressing a control or TAL1 shRNAs were plated in RPMI with 5% FBS, and the cell numbers were measured daily using an MTT-based assay.