Fig. 1. CSA is recruited to DNA damage-stalled RNAPIIo by CSB.

a Outline of a new IP method to isolate RNAPIIo and associated proteins from mock-treated or UV-irradiated (20 J/m²) U2OS (FRT) cells. b Endogenous RNAPII Co-IPs on WT cells stained for the indicated TCR proteins. Note that it is not possible to stain for all these proteins on one membrane. This panel is a composite of several representative Co-IPs. See Supplementary Fig. 1a for each individual Co-IP. c Endogenous RNAPII Co-IP followed by slot blot analysis of CPDs d Western blot analysis of CSA, CSB, and UVSSA knockout cells complemented with inducible GFP-tagged versions of these proteins (n = 2). See Supplementary Fig. 2a, b for validation of knockouts by sequencing. e Clonogenic Illudin S survival of WT, CSA, CSB, and UVSSA knockout and rescue cell lines. Each symbol represents the mean of an independent experiment (n = 2 for all except for WT in UVSSA-KO figure which is n = 3) each experiment contains two or three technical replicates. Endogenous RNAPII Co-IP on f WT, CSA, CSB, and UVSSA knockout cells, g CSB-KO stably expressing GFP-CSB, and h WT, XPC, CSA, CSB, and UVSSA knockout cells. The asterisk in e indicates the heavy chain of the RNAPII antibody. At least two independent replicates of each IP experiment were performed obtaining similar results. Source data are provided as a Source Data file.