The transcription-repair coupling factor (TRCF, product of the mfd gene) couples transcription and DNA repair in bacteria. TRCF removes transcription elongation complexes stalled at DNA lesions and recruits the nucleotide excision repair (NER) machinery to the site. This protein, comprised of eight domains, including region of structurally similar to UvrB, shows to distinct activities: the relief of transcription-dependent inhibition of nucleotide excision repair (NER) by recognition and ATP-dependent removal of a stalled RNAP covering the damaged DNA; and the stimulation of DNA repair by recruitment of the Uvr(A)BC endonuclease.

Structural domains comprising this superfamily share the structure of the C-terminal D7 (handle) domain of TRCF, whose precise role is yet to be clarified although some insights have been revealed. Most residues conserved between TRCF and UvrB in the putative UvrA binding surface are buried in the D2/D7 interface and are thus not available for binding UvrA. It is believed that once TRCF engages with the stalled RNAP and displaces it, an RNAP-triggered conformational change in TRCF moves D7 relative to D2, unmasking the putative UvrA binding surface. This enables the recruitment of Uvr(AB) via UvrA binding to D2. Overall, D7 appears to block the otherwise deleiterious interaction between TRCF and UrvA until a conformational change in the former, during its functional cycle, unmasks the UvrA binding determinant PMID:16469698.