INVESTIGATING THE ROLES OF LIPIN PHOSPHATASE Spo7-Nem1 AND LIPID FLUX IN MITOTIC NUCLEAR ENVELOPE REMODELLING

Abstract

In this thesis, we characterized the positive regulator of lipin activity, the lipin phosphatase complex Spo7-Nem1, as well as the distribution of the substrate and product of lipin, phosphatidic acid and diacylglycerol, in the two fission yeast species. We have also developed a set of PA and DG probes for use in fission yeasts, allowing us to track changes in the distribution and levels of PA and DG with a spatial and temporal resolution. Our results indicate that the Spo7-Nem1 phosphatase complex from the two related fission yeast species have divergent properties. The loss of Spo7, Nem1 and Ned1 resulted in differing responses in S. pombe and S. japonicus including cellular lipidome changes, protein stability, oxidative stress tolerance, hyphae transition and lipid droplet morphology. We also identified a novel role of the diacylglycerol kinase Dgk1, which catalyzes the reverse reaction of lipin, during mitosis in S. pombe.