Fig. 3: DGCR8 promotes the recruitment of RNF168 to RNF8 and MDC1 at DSBs, histone ubiquitination, and DNA repair upon irradiation.

a Immunoblotting of Drosha, DGCR8, and β-actin in the LM2-DRR (expressing the pLCN DSB Repair Reporter) cell line transduced with DGCR8 shRNA. b Knockdown of DGCR8 decreased HR and NHEJ efficiency in LM2-DRR cells. Two days after co-transfection of I-SceI endonuclease and an exogenous donor for HR (pCAGGS DRR mCherry Donor EF1a BFP) into the DGCR8-knockdown LM2-DRR cells, the percentages of GFP-positive and mCherry-positive cells, gated on BFP-positive cells, were determined by flow cytometry. Repair by HR or NHEJ leads to mCherry or GFP expression. Data were normalized to the control cells. n = 3 biological replicates. c MYC-DGCR8-overexpressing LM2 cells were treated with IR (8 Gy) and cultured for 1 h, followed by pulldown with MYC beads and immunoblotting with the indicated antibodies. d Control and DGCR8-knockdown LM2 cells were treated with IR (8 Gy) and cultured for 1 h, followed by immunoprecipitation with an antibody against RNF168 or RNF8 and immunoblotting with the indicated antibodies. e Chromatin was extracted from LM2 cells that were treated with IR (8 Gy) and cultured for 1 h. The chromatin fractions, with or without MNase treatment, were immunoprecipitated with a DGCR8-specific antibody and immunoblotted with the indicated antibodies. f Quantification of MDC1, RNF8, RNF168, 53BP1, and BRCA1 foci in DGCR8-knockdown LM2 cells. Cells were incubated for 1 h after 2-Gy IR and immunostained with antibodies against γH2AX, MDC1, RNF8, RNF168, 53BP1, and BRCA1 (see representative images in Supplementary Fig. 3). n = 3 biological replicates. g Control and DGCR8-knockdown LM2 cells with stable overexpression of FLAG-H2A and RNF8 or RNF168 were transfected with HA-ubiquitin (Ub), treated with IR (8 Gy), and cultured for 8 h, followed by immunoprecipitation with anti-FLAG beads and immunoblotting with antibodies against HA and FLAG. Before immunoprecipitation, lysates were heated at 95 °C for 5 min in the presence of 1% SDS (for denaturing), followed by a 10-fold dilution with lysis buffer and sonication. LE long exposure, SE short exposure. Statistical significance in b and f was determined by a two-tailed unpaired t-test. Error bars are mean ± SEM. n.s. not statistically significant. Source data are provided as a Source Data file.