Fig. 4.

c-Myc is downstream of the Paf1 complex in the control of cell proliferation. (A) c-myc expression in HeLa cells treated with 80 nM of c-myc siRNA in the presence of control, HRPT2- or Paf1-specific siRNA. Efficacy of RNAi-mediated gene silencing of c-myc (Top Panel), HRPT2 (Second Panel) and Paf1 (Third Panel) were assessed by immunoblot analysis. (B) For the cell proliferation assay, HeLa cells were treated with control siRNA, HRPT2- or Paf1-specific siRNA in the absence or presence of 80 nM of c-myc-specific siRNA. Forty-eight hours after treatment, proliferation was estimated by a colorimetric assay as described in Methods. Data are representative of three individual repeats with similar results. (C) c-Myc expression in HeLa cells treated with control-, HRPT2- or Paf1-specific siRNA in the presence of 0, 20, or 40 nM of c-myc-specific siRNA. Gene silencing efficiency of c-myc (Top Panel), HRPT2 (Second Panel) and Paf1 (Third Panel) are monitored by Western blot analysis. (D) Cell proliferation of HeLa cells after treatment for 48h with HRPT2- or Paf1-specific siRNA in the presence of 0, 20, or 40 nM of c-myc-specific siRNA was estimated by a colorimetric assay. Data are representative of three independent experiments with similar results. Significance of the differences were evaluated by Student's t test (**, P < 0.01, *, P < 0.05). In A and C the expression of β-actin is shown as a loading control.