Complementary roles of yeast Rad4p and Rad34p in nucleotide excision repair of active and inactive rRNA gene chromatin

Mol Cell Biol. 2008 Dec;28(24):7504-13. doi: 10.1128/MCB.00137-08. Epub 2008 Oct 20.

Abstract

Nucleotide excision repair (NER) removes a plethora of DNA lesions. It is performed by a large multisubunit protein complex that finds and repairs damaged DNA in different chromatin contexts and nuclear domains. The nucleolus is the most transcriptionally active domain, and in yeast, transcription-coupled NER occurs in RNA polymerase I-transcribed genes (rDNA). Here we have analyzed the roles of two members of the xeroderma pigmentosum group C family of proteins, Rad4p and Rad34p, during NER in the active and inactive rDNA. We report that Rad4p is essential for repair in the intergenic spacer, the inactive rDNA coding region, and for strand-specific repair at the transcription initiation site, whereas Rad34p is not. Rad34p is necessary for transcription-coupled NER that starts about 40 nucleotides downstream of the transcription initiation site of the active rDNA, whereas Rad4p is not. Thus, although Rad4p and Rad34p share sequence homology, their roles in NER in the rDNA locus are almost entirely distinct and complementary. These results provide evidences that transcription-coupled NER and global genome NER participate in the removal of UV-induced DNA lesions from the transcribed strand of active rDNA. Furthermore, nonnucleosome rDNA is repaired faster than nucleosome rDNA, indicating that an open chromatin structure facilitates NER in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatin / genetics
  • Chromatin / metabolism*
  • DNA Repair*
  • DNA, Ribosomal / genetics
  • DNA, Ribosomal / metabolism
  • DNA, Ribosomal / radiation effects
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • DNA-Directed RNA Polymerases / genetics
  • DNA-Directed RNA Polymerases / metabolism
  • Genes, rRNA*
  • Humans
  • Nucleosomes / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Transcription Initiation Site

Substances

  • Chromatin
  • DNA, Ribosomal
  • DNA-Binding Proteins
  • Nucleosomes
  • RAD34 protein, S cerevisiae
  • Rad4 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • DNA-Directed RNA Polymerases