Nucleotide excision repair in yeast

Abstract

Nucleotide Excision Repair (NER) is a conserved DNA repair pathway capable of removing a broad spectrum of DNA damage. In human cells a defect in NER leads to the disorder Xeroderma pigmentosum (XP). The yeast Saccharomyces cerevisiae is an excellent model organism to study the mechanism of NER. The yeast proteins Rad4 and Rad23 are important in NER and involved both Transcription-Coupled and Global Genome NER sub-pathways. Chapter 2 describes a novel mechanism of generegulation by the GG-NER E3 ligase. This protein complex can regulate dNTP synthesis via UV-induced Rad4 ubiquitination. In Chapter 3 we describe the effect of this histone on TC-NER at the rDNA. We find that Rad34 is only required when Histone H1 is present. In Chapter 4 we analyze the phenotype of a yeast strain containing a RAD4 mutation. The mutation affects a conserved residue that when altered in the human homolog XPC, leads to the cancer prone disorder XP. Chapter 5 is dedicated to the Rad4-Rad23 interaction that we describe in more detail. We uncovered a novel N-terminal interaction of Rad23 with Rad4 that is important for TC-NER. Finally, in Chapter 6 we reveal an unexpected UV phenotype for the commonly used wild-type yeast strain WCG4A. In this strain we identified the mutation to reside in the RAD4 gene