ARF3 and Cell Polarity in Budding Yeast 

Abstract  

The budding yeast  S. cerevisiae  reproduces by forming a small bud that gradually enlarges as the cell progresses through the cell cycle. In yeast, bud formation occurs in a specific pattern, and this polarized type of cell division is a model for understanding fundamental aspects of how cell polarity is established. Cell polarity is important for the structure and function of single-celled organisms, like yeast, and multicellular organisms, like humans. During yeast cell division, the new bud usually forms directly adjacent to the previous bud in haploid yeast cells.  ARF3  is a gene in yeast—a member of the small GTPase family of proteins. ARF proteins are important for membrane trafficking events, such as endocytosis, in yeast and other species. In yeast, Arf3p localizes to the bud site during cell division in yeast. Mutant yeast cells that contain a deletion of ARF3 (arf3Δ) exhibit a budding polarity defect. However, the role that Arf3p plays in establishing bud site polarity is unknown. Dr. Schweitzer is interested in investigating the function of Arf3p during polarized cell division in yeast. During summer 2021, she examined budding polarity in arf3Δ yeast. After reproducing the reported budding polarity defect in arf3Δ yeast, she investigated budding polarity in two other yeast mutant strains, drs2Δ and cdc50Δ.  DRS2 and CDC50 interact genetically with ARF3 and play a role in changing the local composition of the plasma membrane. Here, she describes data showing that when either of these genes is knocked-out, yeast exhibit a budding polarity defect.  

Biographical Statement 

Jill Schweitzer has taught at IU East for six years, starting part-time in 2015 and now as an Assistant Professor. Courses taught include introductory biology, molecular biology, immunology, and biochemistry. Her research utilizes S. cerevisiae (budding yeast) and fluorescence microscopy to study polarized cell division. While many proteins regulate bud site selection, the Schweitzer lab is interested in studying the role of proteins involved in membrane trafficking and polarized cell division, particularly Arf3p. This research combines skills that Schweitzer gained during her graduate work at the University of Minnesota and her post-doctoral research at the University of Notre Dame. As a graduate student, Schweitzer used the power of yeast genetics to study the instability of DNA trinucleotide repeat sequences associated with neurodegenerative diseases, such as Huntington’s Disease. As a postdoctoral fellow, Schweitzer used fluorescence microscopy and other techniques to investigate the role of mammalian Arf6 in cell division, specifically cytokinesis, and in lipid trafficking. Now, she is pursuing research that will elucidate the role of Arf3p (the yeast homolog of mammalian Arf6) during polarized cell division in yeast. Outside of the lab and classroom, Schweitzer co-parents three teenagers, Luke, Ben, and Anna, with her husband, Steven. Schweitzer enjoys discussing issues of science and faith, and she has spoken and taught about the intersection of science and religion in current culture.