The integrity of DNA is constantly threatened by large number of exogenous and endogenous agents of both chemical and physical nature. Living cells therefore posses several DNA repair mechanisms,... Show moreThe integrity of DNA is constantly threatened by large number of exogenous and endogenous agents of both chemical and physical nature. Living cells therefore posses several DNA repair mechanisms, that can detect and repair damaged DNA. One such mechanism is Nucleotide Excision Repair (NER). NER detects damaged DNA and subsequently removes a ~30nt oligonucleotide containing the damage. Repair is completed by synthesizing new DNA using the undamaged strand as a template. This thesis is focussed on the damage recognition step of NER, using the yeast Saccharomyces cerevisiae as a model organism. The Rad4 protein functions as a damage-sensor for NER. Here, experiments are described which show that two previously unidentified proteins, now named Rad33 and Rad34, are also involved in damage recognition. Rad34 is a Rad4 homologue specifically involved in NER in the ribosomal DNA (rDNA) region. Rad33 is a small protein that binds to Rad4 and to Rad34 and is essential for proper functioning of these proteins in NER. Further studies reveal that Rad33 is involved in regulating post-translational modifications of Rad4 and that Rad33 shows functional resemblance to the human Centrin2 protein, which functions in complex with the human Rad4 homologue XPC. Show less
