clk-1 encodes a hydroxylase that is necessary for ubiquinone (UQ) biosynthesis. clk-1 mutants do not synthesize UQ, but instead accumulate the precursor demethoxyubiquinone (DMQ). When fed on bacteria that synthesize UQ the mutants are viable but display slow development, behaviours and aging. However, they arrest development when fed on UQ synthesis-deficient bacteria. I have taken a genetic suppressor approach to investigate the causes of the various phenotypes as well as of the dietary requirements of the clk-1 mutants. / We identified two classes of mutants that suppress the defecation phenotypes of clk-1. All of these "dsc" mutants suppress the lengthened cycle of clk-1. Class I mutants also restore the ability to react normally to changes in temperature whereas the Class II mutants do not. The characterization of the Class I mutants suggests that part of the phenotype of clk-1 is due to an alteration of lipid metabolism, likely the level of lipid or lipoprotein oxidation. dsc-4 encodes the worm homolog of the Microsomal Triglyceride Transfer Protein (MTP), a protein required for the formation of low density lipoproteins (LDL) in vertebrates, and whose absence in people leads to abetalipoproteinemia. dsc-3 appears to be allelic to tat-2, which encodes a type IV P-type ATPase that is related to a family of human aminophospholipid transporters that includes ATP8B1/FIC1, whose inactivation results in cholestatic liver disease. dsc-3 and dsc-4 appear to affect distinct aspects of lipid metabolism. A general link between the Class II mutants and clk-1 remains elusive. dsc-1, a Class II gene, encodes a paired-like homeodomain transcription factor that is necessary for the GABA sensitivity of enteric muscles. / We also identified 9 clk-1(e2519)-specific suppressors, which suppress most Clk phenotypes, including their requirement for dietary UQ. Our analysis of these suppressors reveals that it is the lack of UQ rather than the presence of DMQ that is responsible for most phenotypes. In addition, they allowed us to show that most Clk phenotypes can be uncoupled from each other. We cloned six suppressors and all encode missense tRNA(Glu) suppressor genes. To my knowledge, these represent the first missense tRNA suppressors identified in any metazoan.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.100328 |
| Date | January 2006 |
| Creators | Branicky, Robyn. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | © Robyn Branicky, 2006 |
| Relation | alephsysno: 002341478, proquestno: AAINR25107, Theses scanned by UMI/ProQuest. |
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