BRCA2 promotes R-loop resolution by DDX5 helicase at DNA breaks to facilitate their repair by homologous recombination (2021)
Figure 7

Figure 7. BRCA2-T207A bearing cells exhibit reduced localization of DDX5 at DSB-associated DNA-RNA hybrids.

(A) Top: Representative images of In situ PLA performed between DDX5 and S9.6 (DNA-RNA hybrids) antibodies in BRCA2 deficient DLD1 cells (BRCA2-/-) or DLD1 stable clones expressing BRCA2 (WT) or BRCA2-T207A (T207A). Cells were fixed directly or 4h post-irradiation (6Gy). When indicated, cells were transfected/treated with RNase H1 (RH) prior to fixation. Single antibody controls in non-irradiated BRCA2 WT cells are shown. Scale bar indicates 10 µm. Bottom: Quantification of the number of PLA spots per nucleus. At least 500 cells were counted per condition from three independent experiments. For statistical comparison of the differences between the samples we applied a Kruskal-Wallis test followed by Dunn's multiple comparison test and the p-values show significant differences. The red line in the plot indicates the median and each symbol represents a single PLA spot.

(B) Top: Representative images of In situ PLA performed between DDX5 and γH2AX antibodies in BRCA2 deficient DLD1 cells (BRCA2-/-) bearing BRCA2 (WT) or BRCA2-T207A (T207A). Cells were fixed directly or 4h post-irradiation (6Gy). When indicated, cells were transfected/treated with RNase H1 (RH) prior to fixation. Single antibody controls in non-irradiated BRCA2 WT cells are shown. Scale bar indicates 10 µm. Bottom: Quantification of the number of PLA spots per nucleus. At least 600 cells were counted per condition from three independent experiments. For statistical comparison of the differences between the samples we applied a Kruskal-Wallis test followed by Dunn's multiple comparison test and the p-values show significant differences. The red line in the plot indicates the median and each symbol represents a single PLA spot.

(C) Left: Representative images of the recruitment of transient transfected GFP-MBP-BRCA2 (WT and T207A) to DNA damage tracks at 5 min post-irradiation in U2OS cells. γH2AX is used as a marker of DNA damage. Scale bar indicates 10 µm. Right: Quantification of the intensity of GFP signal at the laser tracks. At least 130 cells were counted per condition from three independent experiments. For statistical comparison of the differences between the two samples we applied an unpaired t-test. The red line in the plot indicates the median and each symbol represents a single cell intensity value.

(D) Top: Representative images of in situ PLA performed between S9.6 (DNA-RNA hybrids) and anti-γH2AX antibodies in BRCA2 deficient DLD1 cells (BRCA2-/-) bearing BRCA2 (WT) or BRCA2-T207A (T207A). When indicated, cells were transfected/treated with RNase H1 (RH) or treated with Cordycepin (Cordy) for 2h at 37°C before fixation. Single antibody controls in non-irradiated BRCA2 WT cells are shown. Scale bar indicates 10 µm. Nuclei as defined by auto threshold plugin on the DAPI image (Image J) our outlined in yellow. Bottom: Quantification of the number of PLA spots per nucleus. At least 600 cells were counted per condition from three independent experiments. For statistical comparison of the differences between the samples we applied a Kruskal-Wallis test followed by Dunn's multiple comparison test and the p-values show significant differences. The red line in the plot indicates the median and each symbol represents a single PLA spot.

(E) Top: PAGE gel showing a representative unwinding assays in which purified MBP-DDX5-GST (1-5 nM) was incubated with 32P-labelled synthetic R-loop substrate in presence or absence of 50 nM purified BRCA2T1-T207A (bottom right). Bottom left: Quantification of the unwinding experiments showing the percentage of free RNA relative to the R-loop substrate (unwound product) as a function of DDX5 concentration alone (black) or in presence of BRCA2T1-T207A (green). The data represent the mean ± SD of at least three independent experiments. Bottom right: SDS-PAGE showing 650 ng of purified 2XMBP-BRCA2T1-T207A used in the unwinding assay.