Transcription-coupled DNA repair targets DNA lesions that block progression of elongating RNA polymerases. In bacteria, the transcription-repair coupling factor (TRCF; also known as Mfd) SF2 ATPase recognizes RNA polymerase stalled at a site of DNA damage, removes the enzyme from the DNA, and recruits the Uvr(A)BC nucleotide excision repair machinery via UvrA binding. Previous studies of TRCF revealed a molecular architecture incompatible with UvrA binding, leaving its recruitment mechanism unclear. Here, we examine the UvrA recognition determinants of TRCF using X-ray crystallography of a core TRCF-UvrA complex and probe the conformational flexibility of TRCF in the absence and presence of nucleotides using small-angle X-ray scattering. We demonstrate that the C-terminal domain of TRCF is inhibitory for UvrA binding, but not RNA polymerase release, and show that nucleotide binding induces concerted multidomain motions. Our studies suggest that autoinhibition of UvrA binding in TRCF may be relieved only upon engaging the DNA damage.cysteine cross-linking | transcription | ATPase stimulation | UvrB R NA polymerase (RNAP) stalled at DNA lesions on the transcribed strand elicits a preferential pathway for nucleotide excision repair (NER) called transcription-coupled repair (TCR), which is present in Bacteria and Eukarya (1). Bacterial transcription-repair coupling factor (TRCF; also known as Mfd) orchestrates this process by specific recognition of the transcription and NER assemblies, which reflects its twofold role. First, TRCF relieves transcription-dependent NER inhibition due to occlusion of the DNA lesion by RNAP (2). TRCF, an SF2 ATPase with dsDNA translocase but no helicase activity (3), approaches the stalled RNAP from behind and induces its forward translocation by stepping on dsDNA using ATP hydrolysis (4, 5). The consequent collapse of the upstream end of the transcription bubble leads to massive destabilization of the otherwise stable ternary elongation complex (TEC) and transcription termination (4-7). Rho, the only other known bacterial enzymatic terminator, induces termination by a similar forward-translocation mechanism, but translocates along the nascent RNA (8). Second, TRCF recruits the Uvr(A)BC endonuclease to the unmasked lesion by binding to UvrA (4, 9). This initiates a cascade of events resulting in lesion excision and gap filling (4, 10). TRCF also has roles beyond TCR-in the rescue of replication forks stalled by head-on collisions with RNAPs (11), in the development of antibiotic resistance (12, 13), recombination (14, 15), and transcriptional regulation (16, 17).The crystal structure of apo TRCF (18) revealed a multimodular enzyme with eight domains connected by flexible linkers (Fig. 1A), an architecture that appears primed for large conformational changes, which are believed to be critical for coupling RNAP recognition to recruitment of NER enzymes. Domains D1 and D2 of TRCF are similar to the NER protein UvrB, which also binds UvrA (18,19), suggesting that these domains serve as a pl...