The kinase activity of mTOR is essential for translational control of TOP mRNAs.

<p>(A) HEK293 cells were transfected with vectors expressing mTOR-wt, mTOR-rr or mTOR-rr-kd, two days later the cells were amino acid-starved for 3 h followed by 3 h refeeding without or with 20 nM rapamycin. Cytoplasmic proteins derived from the cells were subjected to Western blot analysis with the indicated antibodies. B) Cytoplasmic extracts derived from cells treated as described in (A), were subjected to polysomal analysis. C) HEK293 cells were amino acid-starved for 3 h, or amino acid-starved for 3 h followed by 3 h refeeding without or with 50 nM Torin1. Cytoplasmic proteins derived from the cells were subjected to Western blot analysis with the indicated antibodies. D) Cytoplasmic extracts derived from cells treated as described in (C) were subjected to polysomal analysis and the percentage of mRNA in polysomes is presented as an average ± SEM of three experiments.</p>