MOLECULAR BIOLOGY OF MITOSIS IN ASPERGILLUS

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Mitosis and its regulation are of fundamental importance to understanding cell biology, cancer, and human development. The morphological and biochemical features of mitosis are highly conserved among eukaryotic organisms. For this reason the use of lower eukaryotes, e.g. yeasts and fungi to study the genetics of mitosis has been highly productive. Here we propose to study the bimE gene of Aspergillus and its gene product, which has been shown in previous experiments to be an important negative regulator of mitosis and appears to be part of a regulatory system that prevents mitosis if DNA synthesis has not been completed. We will generate and use antibodies to bimE/E. coli trypE or lacZ fusion proteins to characterize the bimE gene product through the cell cycle in synchronized cells, looking for changes in its synthesis, biochemical structure, post- translational modification, localization and interactions with other proteins. We also propose to characterize proteins with which the bimE protein might interact by analysis of indirect suppressor and unlinked noncomplementing mutations. We will attempt to learn how bimE regulates the level of nimA mRNA by determining the effect of bimE on transcription and/or stability of nimA mRNA. Finally, in collaboration with Dr. John Newport of UC-San Diego we will look for a functional homolog of bimE in Xenopus laevis nad study the effect of the bimE gene product on mitosis in the Xenopus egg cytoplasm cell-free system.