Journal: bioRxiv
Article Title: Parp7 generates an ADP-ribosyl degron that controls negative feedback of androgen signaling
doi: 10.1101/2024.12.21.629908
Figure Lengend Snippet: DTX2 is the E3 ligase for ADP-ribosylated AR. A, Immunoblot detection of Flag-AR and AR-ADPr (by FL-AF1521) in PC3-AR cells with siRNA knockdowns (total 4-day knockdown) of the selected relevant E3 ligases (DTX1, DTX2, DTX4, HUWE1, RNF146, SPOP, TRIP12 and UBR5), treated with R1881 for 21 hr before cell harvest. The AR/TUB and AR-ADPr/AR ratios for each lane are presented below the blot. B, Immunoblot detection of Flag-AR and AR-ADPr in PC3-AR cells with siDTX2 knockdown, treated with R1881 for times indicated on the panel. The AR-ADPr/AR ratio for each lane is presented below the blot. C, Immunoblot detection of Flag-AR and AR-ADPr in PC3-AR siCTRL and siDTX2 cell extracts and AF1521 bound fraction. Cell extracts from PC3-AR siCTRL and siDTX2 cells treated with R1881 for 6 hr were combined with AF1521 beads for the enrichment of ADP-ribosylated proteins. D, Immunoblot detection of Flag-AR and AR-ADPr in PC3-AR siCTRL/siDTX2 and PC3-AR HA- PARP7 cell extracts and GSH beads bound fraction. Cell extracts from PC3-AR siCTRL/siDTX2 and PC3-AR HA-PARP7 cells treated with R1881 for 6 hr were combined with GSH beads loaded with GST- DTX2-RD or GST-DTX2-RD mut for the enrichment of proteins recognized by DTX2 DTC domain. E, Diagrams of DTX2-RD and DTX2-RD mut . Three loss of function mutations in the DTC domain of DTX2-RD mut (S568A, H582A, and H594A) are indicated with red asterisk. F, Schematic diagram of AR protein preparation as a substrate for biochemical reactions. Cell extracts from PC3-AR siDTX2 cells treated (left) or untreated (right) with R1881 for 6 hr were combined with M2 beads for immunoprecipitation. The purified protein from the preparation with R1881 treatment was used for experiments in panels G and H, and the purified protein from the preparation without R1881 treatment was used only in panel H. G, Immunoblot detection of Flag-AR and AR-ADPr from the ubiquitylation assay on AR protein prepared with siDTX2 and R1881 treatment (panel F, left). The ubiquitylated products (Ub product, red bracket) are labeled for Flag-AR and AR-ADPr detection. All reactions contained AR-ADPr (R1881 treated samples), ATP, Ub, E1 and E2. For DTX2-RD status (dropout or DTX2-RD mut ), refer to labels. H, Immunoblot detection of Flag-AR, AR-ADPr, and GST-DTX2-RD from the ubiquitylation assay on AR protein prepared with siDTX2 transfection, and with or without R1881 treatment (panel F). The ubiquitylated products (Ub product) are labeled in red for Flag-AR and AR-ADPr detection. The dropouts of the ubiquitylation assay components (Ub, E1, E2, and 30°C incubation) are indicated on the labels. The T7-Ubiquitin (T7-Ub) was detected by Ponceau staining. Lane numbers are indicated below the blot. I, Bar plots showing the results of an RT-qPCR experiment in PC3-AR siCTRL/siDTX2 cells untreated (grey), treated with R1881 (purple), and cotreated with R1881 and RBN2397 (blue). The y-axis represents the relative expression normalized to the GUS housekeeping gene, and the x-axis represents the siRNA used. The p-values from the Welch’s t-test for comparisons between corresponding conditions in siCTRL and siDTX2 are indicated on the plots. Error bars represent standard deviation (n = 3; n represents number of biological replicates).
Article Snippet: Ubiquitylation assays were performed at 30°C for 30 min with 1 mM ATP, 100 g/ml Ub (T7-Ub or bovine Ub (Sigma U6253)), 5 g/ml each of UB E1 (R&D Systems E-304) and UB E2 (His-UbcH5C, R&D Systems E2-627), and 20 g/ml GST-DTX2 RD in the buffer E (20 mM Tris-HCl pH 7.5, 50 mM NaCl, 2 mM MgCl2, 1 mM DTT, 1 µg/ml each of A/L/P and 0.1 mg/ml BSA).
Techniques: Western Blot, Knockdown, Immunoprecipitation, Purification, Ubiquitin Assay, Labeling, Transfection, Incubation, Staining, Quantitative RT-PCR, Expressing, Standard Deviation