Fig. 1. Identification of conserved RPA-binding motifs in the BTR complex.

a Schematic of proteins, domains, and motifs in the BTR complex. TR TOP3A-RMI1-binding domain, DHBN dimerization helical bundle in N-terminal, RQC RecQ C-terminal, HRDC helicase and RNaseD C-terminal; 3H 3-helix bundle, OB oligonucleotide-binding. b Plots of MS hits from peptide pulldowns with motifs 1, 3, and 5, ranked by emPAI score¹¹⁶ (number of unique peptide sequences adjusted for protein size). RPA subunits are highlighted in red. c Validation of MS results by western blotting, showing that RPA from HeLa nuclear extracts is specifically pulled down by biotinylated peptides based on motifs 1, 3, and 5 but not motifs 2 and 6. d GFP-pulldowns from 293FT cells transfected with constructs expressing GFP or the indicated GFP-tagged RMI1 variants, showing that loss of motif 5 disrupts RPA-binding. e GFP-pulldowns from 293FT cells transfected with constructs expressing either GFP or GFP-RPA1, and the indicated FLAG-tagged BLM variants, showing how loss of motifs 1 and/or 3, and the N-terminal TOP3A-RMI1 (TR) binding domain of BLM impacts on RPA-binding.