Molecular mechanism of transcription-repair coupling.
Lesions in the transcribed strand block transcription and are repaired more rapidly than lesions in the nontranscribed (coding) strand which do not block RNA polymerase (RNAP). It has been shown previously that in Escherichia coli the mfd (mutation frequency decline) gene is necessary for strand-specific repair. The mfd gene was cloned and sequenced and the Mfd protein was purified and used to reconstitute strand-specific repair in a completely defined system. The mfd gene encodes a protein of 130 kilodaltons and contains the so-called "helicase motifs," a leucine zipper motif, and regions of sequence similarity to UvrB and RecG proteins. The Mfd protein was shown to (i) displace RNAP stalled at a lesion in an adenosine triphosphate-dependent reaction, (ii) bind to the damage recognition subunit (UvrA) of the excision nuclease, and (iii) stimulate the repair of the transcribed strand only when transcription is taking place. Thus, Mfd appears to target the transcribed strand for repair by recognizing a stalled RNAP and actively recruiting the repair enzyme to the transcription blocking lesion as it dissociates the stalled RNAP.
Selby
C P
CP
Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill 27599.
Sancar
A
A
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004265:DNA Helicases; D004260:DNA Repair / Q000235:genetics*; D004269:DNA, Bacterial / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D016350:Leucine Zippers; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics; D009154:Mutation / Q000235:genetics; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes; D014157:Transcription Factors; C058093:UvrB protein, E coli; C072103:transcription repair coupling factor protein, Bacteria; C071446:RecG protein, E coli; D012321:DNA-Directed RNA Polymerases; D004706:Endodeoxyribonucleases; C036385:endodeoxyribonuclease uvrABC; D004265:DNA Helicases