Abasic sites in the transcribed strand of yeast DNA are removed by transcription-coupled nucleotide excision repair.
Abasic (AP) sites are potent blocks to DNA and RNA polymerases, and their repair is essential for maintaining genome integrity. Although AP sites are efficiently dealt with through the base excision repair (BER) pathway, genetic studies suggest that repair also can occur via nucleotide excision repair (NER). The involvement of NER in AP-site removal has been puzzling, however, as this pathway is thought to target only bulky lesions. Here, we examine the repair of AP sites generated when uracil is removed from a highly transcribed gene in yeast. Because uracil is incorporated instead of thymine under these conditions, the position of the resulting AP site is known. Results demonstrate that only AP sites on the transcribed strand are efficient substrates for NER, suggesting the recruitment of the NER machinery by an AP-blocked RNA polymerase. Such transcription-coupled NER of AP sites may explain previously suggested links between the BER pathway and transcription.
Kim
Nayun
N
Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 2771, USA.
Jinks-Robertson
Sue
S
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D004249:DNA Damage; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
D004271:DNA, Fungal; C072975:RAD14 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D004706:Endodeoxyribonucleases; C083274:Apn1 protein, S cerevisiae; D000251:Adenosine Triphosphatases; C465758:RAD26 protein, S cerevisiae; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; C101825:NTG1 protein, S cerevisiae; C116827:NTG2 protein, S cerevisiae; D045643:DNA Repair Enzymes