Download or read book Investigation Into Aspects of the DNA Damage Response of Fission Yeast written by and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The maintenance and integrity of the genome is of fundamental importance to all living organisms. The DNA within a cell is subject to a variety of endogenous and exogenous factors which could ultimately lead to alterations in the genetic code. Due to the nature of DNA damage caused by these factors, many organisms have evolved a number of overlapping DNA repair mechanisms that are able to recognise and repair such damage. Mutants defective in these processes have proved useful for the elucidation of the mechanisms involved. The rad32 mutant is sensitive to both UV and gamma irradiation, and has been shown to be defective in meiotic recombination. The first part of this study involved the further characterisation of the role of Rad32. Site-directed mutagenesis was carried out on the regions encoding the conserved phosphodiesterase motifs of Rad32 followed by experiments to elucidate the importance of these residues. The mutagenesis revealed that these residues are essential for the response to DNA damage and are required for the meiotic cycle of the cell. Previous reports suggested that the conserved regions in other phosphodiesterases may be involved in metal ion binding, and from data in this study this appears to be the case. The second part of this study investigated the role of rad32 and other DNA damage response genes in illegitimate recombination in fission yeast. It was found that the rad32 mutant had altered illegitimate recombination with respect to the efficiency of repair and the mechanism of the repair, but the conserved phosphodiesterase motifs were shown not to be required in this process. Of the other mutants tested rad22 and rqh1 appeared to have elevated rates of illegitimate recombination but the molecular mechanism of the repair was found to be similar to wild type cells. The final part of this study investigated the role of a protein containing six BRCT domains. The precise function of BRCT domains remains to be resolved but proteins containing such domains are required for a range of processes involved in DNA metabolism. In this study the gene, brc1, was deleted and the effects on the cell analysed. It was found that the gene is not essential for cell viability or cell cycle checkpoints. The disruption mutant displayed only moderate sensitivity to DNA damaging agents. Epistasis analysis revealed that the protein is likely to be involved in a process requiring rhp51, the homologue of RecA which is required for recombination in E.coli. From the data presented in this study, Brcl may function in the damage tolerance pathway in fission yeast.