Src or Chk1-inhibition correlates with chromatin breakage. (A) DNA bridges in cells transfected with negative siRNA (control), siSrc, or siChk1, or treated with PP2 for 5 h. (B) Percentage of DNA bridges that appear broken. (C and D) γ-H2AX staining (C) and frequency of telophase cells with DNA bridges exhibiting γ-H2AX staining (D). Arrowheads indicate γ-H2AX foci on DNA bridges. (E and F) HeLa cells expressing LAP2b-RFP were analyzed by phase-contrast live-cell imaging (E) or by fluorescence microscopy of fixed samples (F). Time is from the detection of the intercellular canals containing LAP2b-RFP bridges. Intact intercellular canals are indicated by solid arrows, and broken canals are indicated by dotted arrows. Related to Videos 1, 2, and 3. (G) Percentage of LAP2b-RFP–positive bridges that appear broken. Broken DNA or LAP2b bridges are indicated by dotted arrows. Error bars show the SD from the mean from three independent experiments. A minimum of 50 fixed cells with chromatin bridges was analyzed per experiment. ***, P < 0.001 compared with the control. Statistically significant differences were determined by ANOVA and Student’s t test. Bars, 5 µm.