The Mfd Protein is the Transcription-Repair Coupling Factor (TRCF) in Mycobacterium Smegmatis

n vitro and in vivo experiments with Escherichia coli have shown that the Mfd translocase is responsible for transcription-coupled repair which is defined as the faster rate of repair of the transcribed strand than the non-transcribed strand by nucleotide excision repair. Even though the mfd gene is conserved in all bacterial lineages, there is only limited information on whether it performs the same function in other bacterial species. Here, by genome scale analysis of repair of UV-induced cyclobutene dimers we find that the Mfd protein is the Transcription-Repair Coupling Factor (TRCF) in Mycobacterium smegmatis. This finding, combined with the inverted strandedness of UV-induced mutations in wild-type and mfd- Escherichia coli and Bacillus subtilis indicate that the Mfd protein is the universal TRCF in bacteria.