Heterochromatic Genome Stability Requires Regulators of Histone H3 K9 Methylation
Figure 7
dcr-2 mutants display increased spontaneous DNA damage in heterochromatin.
A) Analysis of the ratios of γH2Av foci to total cell numbers at different cell cycle stages are shown for wild type and dcr-2. γH2Av foci in dcr-2 cells only increased during S phase (p<0.05). P values were calculated by Chi-square test. B) The histograms show cell cycle stage analysis of wild type and dcr-2 cells. The percent of G1 cells in the two groups do not differ significantly (p>0.05). The percentage of S phase cells is not significantly lower in dcr-2 compared to wild type (p>0.05), but the percent of wild-type cells in G2 is significantly lower than in dcr-2 (p<0.05). The mitotic index in dcr-2 cells is 11-fold over wild type (p<0.001), and the percent of apoptotic cells (whole nuclei contain TUNEL signals, instead of foci) in dcr-2 is 18-fold over wild type (p<0.001). P values were calculated by Student's t test, and n>1000 cells for each genotype. C) The chart lists the viability of double mutants of dcr-2 with mutations in the DNA damage checkpoint and mitotic checkpoint pathways. Viability was calculated relative to single homozygous checkpoint mutants, which are less viable than dcr-2 single mutants. Progeny counts are in Table S1. P values were calculated by the Chi-square test.