FIGURE 2.

SUMO isoform depletion has no effect on cell cycle progression and DSB repair protein stability. A, endogenous SUMO1, SUMO2/3, or UBC9 was depleted by two rounds of siRNA transfection in HeLa cells. Cell cycle analysis by flow cytometry was carried out at 48, 72, and 96 h after the second transfection. DNA content of the HeLa cells, as determined by staining with propidium iodide, was measured by FACS analysis. B, depletion of SUMO isoforms or UBC9 by two rounds of siRNA transfection was done in HeLa cells as in A. Con, control; S1, SUMO1; S2/3, SUMO2/3. Analysis of immunoblots was applied to measure protein abundance using specific antibody against the DSB repair protein. RNA helicase A (RHA) was used as a loading control, and the positions of the molecular mass markers in kDa are indicated at the left.