siRNA-mediated depletion of selected candidate protein kinases to validate their effect on endogenous Rac1b levels. NCM460 cells were transfected with the indicated siRNA oligonucleotide and analyzed 48 h after. (A) Western blots showing the degree of depletion of the targeted kinases and the corresponding effect on endogenous Rac1b protein (α-tubulin as loading control). Also shown are the protein levels of the remaining identified candidate protein kinases. (B) Quantitative PCR analysis of endogenous Rac1b transcript levels. The ratio of Rac1b over total Rac1 transcripts was calculated and fold changes in relative Rac1b expression were graphically displayed. Note that only depletion of GSK3β and SRPK1 led to decreased Rac1b transcript levels.
