(A) Schematic of DNA-bound TFIIH (DNA damage verification pocket in XPD and DNA 5’-phosphates indicated by purple and orange spheres, respectively) Binding of both XPB and XPD to the damaged strand would lead to extrusion of a bubble when XPD scans in the 5’−3’ direction, while XPB may be stationary or contribute to bubble extrusion if translocating in the 3’−5’ direction (DNA superposed from PDB IDs 6FWR, 5OQJ (Cheng and Wigley, 2018; Schilbach et al., 2017)). (B) Binding of XPB to the undamaged strand would enable the entire complex to scan in 5’−3’ direction, given the opposing polarities of the two ATPases/helicases involved. (C) Model for the assembled repair bubble. Positions of NER factors are approximate. XPG-p62 PH domain interaction according to (Gervais et al., 2004). See Discussion for details.