Figure 4.

ERK1 knockdown in NIH 3T3 cells facilitates growth in colony formation assays, whereas ERK2 knockdown shows inhibitory effects. NIH 3T3 cells were transfected as indicated with the specific shRNA construct (KD) against ERK1 or ERK2 or the corresponding control sequence (ctr), all cloned into the pSUPER_Puro vector; cells were transfected either with shRNA alone or also with an oncogenic form of H-Ras (Ras^Q61L), and colony formation was scored after 10 days. (a) Representative plates; (b) graph of the number of colonies formed (the result of four independent experiments, expressed as mean ± SEM). Asterisks indicate a statistically significant genotype effect calculated from a post-hoc comparison in one-way ANOVA (Scheffe's test: control versus ERK1 KD; control versus ERK2 KD; Ras^Q61L versus Ras^Q61L-ERK1 KD; Ras^Q61L versus Ras^Q61L-ERK2 KD); single asterisk, p < 0.01; double asterisk, p < 0.0001.