To further characterize the molecular underpinnings of a potential role for GLI1 in facilitating re-activation of RNA Pol I, we utilized an approach combining chromatin immunoprecipitation followed by LC–MS (ChIP-MS), wherein, irradiated tumor cells were subjected to ChIP using POLR1A followed by mass spectrometric analysis of proteins that co-immunoprecipitated with POLR1A at the rDNA loci (Supplementary Fig. 6B). The gene discussed is GLI1; the disease is neoplasm.