Fig. 1: PAR-binding ability of PARP13.2 is critical for maintaining stress granule size.

A HeLa wild-type (WT), PARP13 knockout (KO) cells, and KO cells expressing GFP-PARP13.1 and PARP13.2 were treated with 100 µM sodium arsenite for 1 h. Cells were fixed and stained for eIF3b (red) and DAPI (blue) for stress granule analysis. Transfected cells were shown in green. Scale bar, 10 µm. B Stress granule number, mean area, and total area in panel A were quantified by ImageJ. The mean ± s.e. of each parameter was reported from three biological replicates; **p < 0.01, ***p < 0.001, ****p < 0.0001, ns = not significant, two-tailed unpaired Mann–Whitney U test for SG number analysis and two-tailed unpaired Student’s t test for the rest. Number of cells analyzed was provided in Source data. C Diagram of full-length and truncated forms of PARP13. D Wild-type HeLa cells expressing GFP-tagged full-length or truncated PARP13.2 constructs were treated with 250 µM sodium arsenite for 30 min. Cells were fixed and stained for eIF3b (red) and DAPI (blue). Transfected cells were shown in green. The percentage of GFP foci localized to eIF3b in transfected cells was used to measure stress granule colocalization. The bar graph indicates the percentage of mean ± s.e. from three biological replicates. Scale bar, 10 µm. Number of cells analyzed was provided in Source data. E Terminal ADP-ribose binding cavity of PARP13 (PDB: 7TGQ) with key residues highlighted. F Wild-type HeLa cells expressing GFP-tagged wild-type PARP13.2 or mutants were treated with 100 µM sodium arsenite for 1 h. Cells were fixed and stained for eIF3b (red) to visualize stress granules. DAPI (blue) was used for nuclei staining. Transfected cells were shown in green. Scale bar, 10 µm. G Quantification of panel F. GFP channel was used for analyzing stress granule number, mean area, and total area. The mean ± s.e. of each parameter was reported from three biological replicates; **p < 0.01, ****p < 0.0001, ns = not significant, two-tailed unpaired Mann-Whitney U test for SG number analysis and two-tailed unpaired Student’s t test for the rest. Number of cells analyzed was provided in Source data.