Figure 3.

Loss of TopBP1 critically alters chromosomal phenotype. (A) C33a cells were transfected with 1 µg siRNA luciferase control or 1 µg siRNA TopBP1. Thirty two hours post-transfection, cells were harvested, and protein extract was prepared. Protein extracts were Western blotted for TopBP1, and β-actin was used as the loading control. (B) As in (A), C33a cells were transfected. Sixteen hours post-transfection, cells were washed; 0.1 µg/mL colcemid was supplemented for 16 h; and cells were then harvested and prepared for metaphase spread. Slides were stained with DAPI and imaged via confocal microscopy. The image on the left is a representative spread for siRNA luciferase control cells; the image on the right is the representative spread for siRNA TopBP1. (C) Metaphase spreads were quantified and presented as the percent of cells exhibiting gross chromosomal aberrations.