FIG 4 .

cdtB is essential for activation of the host DNA damage response and G₂/M cell cycle arrest. HeLa cells infected with wild-type strains and ΔcdtB isogenic mutants of serotypes Javiana and Montevideo were analyzed for the presence of 53BP1 and γH2AX foci at 48 hpi. (A) Representative images showing 53BP1 and γH2AX foci among HeLa cells infected with a wild-type serotype Javiana strain and a ΔcdtB isogenic mutant. Scale bars, 25 μm. (B) Quantification of the proportion of HeLa cells with both 53BP1 and γH2AX foci; data represent the results for 2 technical replicates from 2 independent experiments for each of the 4 strains (Javiana and Montevideo parent strains and their respective isogenic mutants); error bars represent standard deviations. **, P value < 0.01; *, P value < 0.05. (C) Proportion of HeLa cell populations in the G₂/M phase determined by DNA content analysis using flow cytometry. HeLa cells were infected at 2 multiplicities of infection with either wild-type strains or ΔcdtB isogenic mutants of serotypes Javiana and Montevideo. Cells were fixed at 48 hpi, and DNA content was measured using PI staining. Data represent the averages for both serotypes from 4 independent experiments for each strain. Bars that do not have identical letters represent statistically different values (P < 0.05). Error bars represent standard deviations.