Updated project metadata. We used Targeted RNase H-mediated Extraction of crosslinked RBPs (TREX)to assess the endogenous region-specific binding partners of 45S rRNA in human HCT116 cells. We performed TREX experiments against the full-length 45S, as well as each individual region (5'ETS. 18S, ITS1, 5.8S, ITS2, 28S, and 3'ETS). Extracted proteins from RNase H digested and control cells (4 or 5 replicate per region per condition) were compared, using label-free (LFQ) Quantitative proteomics.