Distinctive Participation of Transcription-Coupled and Global Genome Nucleotide Excision Repair of Pyrimidine Dimers in the Transcribed Strand of Yeast rRNA Genes.

UV light causes the formation of pyrimidine dimers (PDs). Transcription-coupled (TC) nucleotide excision repair (NER) and global genome (GG) NER remove PDs from the transcribed strand (TS) of active genes and the inactive genome, respectively. TC-NER is triggered by elongating RNA polymerases that are blocked at PDs.

Transcription of ncRNAs promotes repair of UV induced DNA lesions in Saccharomyces cerevisiae subtelomeres.

Ultraviolet light causes DNA lesions that are removed by nucleotide excision repair (NER). The efficiency of NER is conditional to transcription and chromatin structure. UV induced photoproducts are repaired faster in the gene transcribed strands than in the non-transcribed strands or in transcriptionally inactive regions of the genome.

The Efficiency of Global Genome-Nucleotide Excision Repair is Linked to the Fraction of Open rRNA Gene Chromatin, in Yeast.

The yeast rDNA locus is a suitable model to study nucleotide excision repair (NER) in chromatin. A portion of rRNA genes is transcribed and largely depleted of nucleosomes, the remaining genes are not transcribed and folded in nucleosomes. In G1-arrested cells, most rRNA genes do not have nucleosomes.

Analyses of rRNA gene chromatin in cell cycle arrested cells.

The existence of two chromatin structures in the rDNA locus was previously demonstrated for a large variety of organisms, ranging from yeast to human. In yeast there are about 150-200 rRNA genes organized in tandem repeats. Almost half of them are transcribed and largely depleted of nucleosomes (active/open), the other half is not transcribed and is assembled in regular arrays of nucleosomes (inactive/closed).