Fig 1: Abraxas limits K63-linked ubiquitin-dependent SLX4/MUS81 recruitment to CPT damage sites.a Increased chromatin-bound MUS81 in Abraxas KO cells was reduced by SLX4 knockdown. Cells transfected with indicated siRNAs were treated with 1 μM CPT for 1 h. Chromatin fraction was isolated for analysis by western blottings. b SLX4 knockdown reduced the elevated RPA32-pS4/8 levels in Abraxas KO treated with CPT. Total lysates were used for western blottings. c K63-linked polyubiquitination is increased in Abraxas KO U2OS cells treated with CPT. WT and Abraxas KO U2OS cells were untreated or treated with 1 μM CPT for 1 h. Total cell lysates and chromatin fractions were prepared from samples for western blottings. K63-linked ubiquitination was detected by antibodies against K63-linked chain. d BRCC36 knockdown leads to increased RPA32-pS4/8 and overloading of SLX4/MUS81 to CPT-damaged chromatin. Total cell lysates and chromatin fractions were prepared from cells transfected with indicated siRNAs and treated with CPT (1 μM, 1 h). e Ubc13 knockdown reduced elevated RPA32-pS4/8 levels and chromatin-bound MUS81 in Abraxas KO cells treated with CPT. f RNF168 knockdown reduced elevated RPA32-pS4/8 levels and chromatin-bound MUS81 in Abraxas KO cells treated with CPT. See also Supplementary Fig. 5.