Using Yeast as a Model Organism to Study the Functional Roles of Histone Acetylation in DNA Excision Repair.

Histone acetylation plays important roles in regulating DNA metabolic processes, including many DNA repair pathways. The nucleotide excision repair (NER) pathway is critical for removing bulky, helix-distorting DNA lesions, such as UV light-induced photoproducts, but the activity of this pathway is significantly inhibited when lesions reside in nucleosomes. Recent studies have indicated that histone acetyltransferase (HAT) activity may be induced in response to UV damage, in order to facilitate the repair of UV-induced lesions in chromatin. Budding yeast (Saccharomyces cerevisiae) is an important model system for studying the functional roles of histone acetylation and HATs in NER, due to the ease of genetically altering HAT activity or acetylated lysine residues in histones. Here, we describe protocols for measuring the repair of cyclobutane pyrimidine dimers (CPDs), the major UV-induced photoproduct, in yeast strains deficient in HAT activity, either due to gene deletion or rapid anchor-away depletion of the HAT enzyme. Methods for measuring CPD repair in bulk chromatin, as well as individual chromatin loci, are detailed below.