9728143 Dolan Phospholipase D (PLD) is an enzyme ubiquitously expressed among organisms from yeast to man. In mammals, PLD is activated by many different mechanisms in response to numerous stimuli. Activating stimuli include growth factors which implicates PLD in the control of cellular proliferation. PLD is also involved in the differentiation of certain mammalian cell types. In the yeast Saccharomyces cerevisiae, the PLD1 gene has been shown to code for a PLD that is activated at both the level of the gene and of the protein. Cells that lack this enzyme are unable to differentiate to form spores, thus implicating PLD in the regulation of a developmental pathway that includes control of cell proliferation. These features of PLD function in both higher and lower organisms indicating that this enzyme plays critical roles in the control of processes that are of paramount importance to the cell. Currently little is known concerning the mechanisms and factors involved in the regulation of yeast PLD1. Preliminary studies from this laboratory indicate that the product of the IME4 gene, which is required for the formation of spores, is able to stimulate PLD1 activity and therefore may be an important regulator of PLD1. Experiments will be done to further characterize the role of IME4 in PLD1 regulation. Since preliminary studies in other labs indicate that PLD1 transcription is induced during sporulation, this investigator will analyze the DNA sequences that control the transcription of the PLD1 gene in order to identify essential regulatory elements. S. Cerevisiae has been an extremely useful model system for the study of signal transduction. The investigation of the regulation of yeast PLD1 and its subsequent use as a paradigm for exploring mammalian PLD action, will facilitate the elucidation of the roles of PLD. The proposed studies will provide strong background information pertaining to the transcriptional regulation of PLD1. The facility of genetic analysis of trans criptional control in yeast will expand our understanding of this aspect of PLD regulation. This research is looking at the regulation of phospholipase D in yeast. PLD is an enzyme which hydrolyzes membrane phospholipids to form phosphatidic acid. In yeast, cells lacking PLD are unable to undergo meiosis and sporulation. In mammals the enzyme is activated by agents which indicate its role in cell proliferation. Since genetic analysis of regulatory processes can be readily done in yeast these studies will provide important basic information about this enzyme. ***
