Fig. 8: Fusion of a SUMO2 to DHX9^K120R bypasses the SUMOylation of DHX9.

a The interactions between different SFB-DHX9 variants and HA-PARP1 constructs were assessed by co-IP. HeLa cells co-transfected with indicated constructs were collected for IP using anti-HA beads. Levels of SFB-DHX9 variants and SUMO2-DHX9^K120R co-precipitated by HA-PARP1 variants were determined and quantified by Western blot. Representative data of two biological replicates. b The association between DHX9 variants and R-loops in DHX9-depleted HeLa cells was assessed by PLA with indicated antibodies. The number of PLA foci (red) per nucleus was quantified by analyzing 150 nuclei in each condition (two-sided Mann-Whitney U test). The black line indicates the median. c The relative R-loop level at the 5’ pause region of β-actin gene was determined by RT-qPCR. The representative bar graph was from three separate experiments. Values are normalized to β-actin in1 and presented as mean ± SEM. d S2-DHX9^K120R improved cell viability. HeLa cells with DHX9 depletion by siRNA were transfected with the indicated constructs for 66 h before collection. Cell counting for each condition in triplicates was obtained. Data are presented as mean ± SEM from three individual experiments analyzed by one-way ANOVA. e A model depicts the role of DHX9 SUMOylation in enhancing the association of DHX9 with R-loops and multiple RNA-processing factors, aiding in R-loop balance and genome stability. Yellow crescent shapes in PARP1 and DDX21 represent SIMs, and circled S symbols represent SUMO modifications. Source data are provided as a Source Data file.