Figure 5.
SF2/ASF promotes expression of an oncogenic isoform of S6K1 and induces eIF4E phosphorylation. (a) MEF, NIH 3T3 and IMR90 cells were transduced with pBABE or SF2/ASF retroviruses and lysed in SDS. Western blotting was carried out using a monoclonal antibody against the N terminus of S6K1 to detect the endogenous isoforms and one against p-catenin as a loading control. (b) NIH 3T3 cells were transduced with pBABE or S6K1 isoform-1 or isoform-2 retroviruses, and lysates were analyzed by western blotting as in a. The S6K1 antibody reacts with both the endogenous and T7-tagged S6K1 isoforms, but the endogenous isoform-2 is not detected in this exposure. (c) Aliquots of cells in b were seeded in soft agar, and colonies were counted 14 d later. Means ± s.d. are shown; *P = 6×10−7 compared to the pBABE control. (d) MEF cells were transduced with the indicated retroviruses and analyzed by western blotting with the indicated antibodies.