Practice question

In bacterial transcription-coupled repair, stalled RNA polymerase at bulky lesion creates roadblock preventing repair access. Transcription-repair coupling factor Mfd, also known as TRCF, ATPase of superfamily 2, binds upstream DNA and uses ATP-driven translocation to displace stalled polymerase. Mfd contains UvrB homology module that directly recruits nucleotide excision repair machinery UvrA2B complex to damage site. By dissociating polymerase and loading Uvr proteins, Mfd couples transcription state to excision repair. MutS acts in mismatch repair, UvrD in unwinding, RecA in recombination, not transcription repair coupling, highlighting Mfd specificity.