| Popis: |
A major component of the predominant DSB repair pathway in mammalian cells is the DNA-dependent protein kinase (DNA-PK) which consists of a catalytic subunit, DNA-PKcs, and a DNA binding component, Ku (A heterodimer of 70 and 80kDa polypeptides). The identification of a putative Ku70 homologue in the budding yeast, Saccharomyces cerevisiae, suggested that Ku function may be conserved in all eukaryotes. The work presented in this thesis describes the identification and characterisation of Ku70 and Ku80 homologues in budding yeast. Through the establishment of a number of in vivo DNA repair assays I have demonstrated a role for yeast Ku in DNA double-strand break (DSB) repair. Indeed I show that yeast Ku is required for a non-homologous DNA end joining (NHEJ) pathway. Using the yeast system, I have implicated and functionally characterised a number of other genes in the Ku-dependent NHEJ pathway including, Rad50p, Mre11p, Xrs2p, Sir2p, Sir3p and Sir4p. In this thesis I also describe the roles performed by Yku70p and Yku80p in telomere length maintenance and in telomeric silencing. Interestingly, Sir2p, Sir3p and Sir4p have previously been implicated in both telomere length maintenance and in telomeric silencing, suggesting that NHEJ repair and a number of telomere functions share common factors. Indeed, I also show that Rad50p, Mre11p and Xrs2p are also required for telomere length maintenance, but not for telomeric silencing. These observations suggest that the function performed by these proteins at the telomere and the DSB may be fundamentally similar. |
