Induction of the Escherichia coli lactose operon selectively increases repair of its transcribed DNA strand

Isabel Mellon, Philip C. Hanawalt

Research output: Contribution to journalArticlepeer-review

499 Scopus citations


NUCLEOTIDE excision repair helps to ameliorate the lethal and mutagenic consequences of DNA damage by removing helix-distorting lesions from cellular genomes1. We have previously analysed the removal of ultraviolet-induced cyclobutane pyrimidine dimers from specific DNA sequences in mammalian cells and demonstrated that transcriptionally active genes are preferentially repaired2-4. Additionally, we found that in rodent and human cells only the transcribed strand of the dihydrofolate reductase gene is selectively repaired5. Transcription is blocked by pyrimidine dimers in template DNA6 and the selective removal of these lesions seems to be important for cell survival after irradiation with ultraviolet light2,7,8. To determine whether this feature of repair is common to prokaryotes and eukaryotes and better to understand its mechanism, we have investigated repair in the two separate DNA strands of the lactose operon of ultraviolet-irradiated Escherichia coli. We find a dramatic difference in the repair of the two strands only when transcription is induced. Most dimers are removed from the transcribed strand of the induced operon within five minutes of irradiation. In the non-transcribed strand, repair is significantly slower and resembles that found in both strands of the uninduced operon. Thus there seems to be a mechanism that couples nucleotide excision repair and transcription.

Original languageEnglish
Pages (from-to)95-98
Number of pages4
Issue number6245
StatePublished - 1989

ASJC Scopus subject areas

  • General


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