FIG 1.
Syk expression protects MCF7 cells from oxidative stress-induced apoptosis and degradation of Bcl-xL mRNA. (A) MCF7-BD cells lacking Syk (−) or stably expressing Syk-EGFP (+) were treated with 5 mM H2O2 for the indicated times. Cell lysates were analyzed by SDS-PAGE and Western blotting with antibodies against PARP (top). The cleaved form of PARP is indicated by the arrow. The expression of Syk-EGFP was visualized by Western blotting of cell lysates (bottom). (B) MCF7-BD cells lacking Syk (−) or stably expressing Syk-EGFP (+) were exposed to 5 mM H2O2 for 30 min (pulse) and then moved to fresh medium for the indicated total incubation times or treated with 5 mM H2O2 for the indicated times. Cell lysates were analyzed by RT-PCR to measure the levels of Bcl-xL and Bcl-xS mRNA (top) or by Western blotting to detect expressed Syk-EGFP (bottom). (C) Comparison of relative levels of Bcl-xL mRNA. Changes in the ratio of Bcl-xL mRNA to Bcl-xS mRNA were normalized to their relative levels of expression in Syk-deficient cells at time zero, which was set equal to a value of 1.0. Bars represent means ± SEMs from three replicate experiments. Significant differences between pairs were determined using an unpaired, two-tailed Student's t test. *, P < 0.01; **, P < 0.005; ***, P < 0.001.