The identification of new regulators of phase II detoxification gene expression by a genome-wide RNAi screen in Caenorhabditis elegans

The phase II detoxification system is an important cellular defence against free radicals and xenobiotics and is induced in response to stress. Conserved bZIP transcription factors such as Nrf2 in mammals and SKN-1 in Caenorhabditis elegans are required for the regulation of phase II detoxification genes including y- glutamine cysteine synthetase (GCS-1). In this thesis a genome-wide RNAi screen was performed to identify new regulators of phase II detoxification gene expression in C. elegans. This screen identified 233 genes which were required for the increased intestinal expression of a phase II reporter gene, Pgcs-1::gfp, in animals lacking the 2-Cys peroxiredoxin PRDX-2. Interestingly, 67 of these genes were also required for induction of Pgcs-1::gfp expression by arsenite in wild-type animals. Amongst these genes, the signalling proteins TIR-1 (Toll and Interleukin Receptor 1 domain protein) and RACK-1 (Receptor for Activated C Kinase) regulated both Pgcs- l::gfp expression and resistance to arsenite in wild-type animals. TIR-1 regulated arsenite resistance upstream of the p38-related PMK-1 MAPK pathway whereas RACK-1 acted via a PMK-1 independent manner to regulate arsenite resistance. Additionally, data presented here suggests that CSN-2 and other subunits of the COP9 signalosome complex are specifically required for the expression of Pgcs- 1::gfp in the absence of PRDX-2. Interestingly, in the course of performing the screen new roles for the C. elegans ASK1 homologue, NSY-1, were discovered. Further analysis revealed that loss of NSY-1 led to increased fecundity, lifespan, size and developmental rate in wild-type animals, identifying previously uncharacterised roles for this protein in C. elegans.EThOS - Electronic Theses Online ServiceGBUnited Kingdo