Charles B. Shuster, PhD New Mexico State University cshuster@nmsu.edu Phone:(505) 646-1325 Personal Website

Title: Characterization of Mob1 Dynamics in Living Cells

Project Description:

Maintenance of chromosomal ploidy during cell division requires a precise coordination of chromosome segregation and cytoplasmic partitioning (cytokinesis) such that the contractile ring does not assemble before the onset of anaphase. Recent studies in both yeast and animal cells have identified a mitotic checkpoint that monitors kinetochore attachment to the mitotic spindle and regulates the onset of sister chromatid segregation and CDK1 inactivation (mitotic exit). In fission yeast, the mitotic checkpoint also regulates a signaling cascade termed the Septation Initiation Network (SIN) that regulates the initiation of cytokinesis. We have begun to characterize a terminal component of the SIN cascade (Mob1) in embryonic- as well as somatic cells, and preliminary data suggest that Mob1 plays a critical role in facilitating the final events of cell division. In addition, we have identified a novel interaction between Mob1 and Protein Phosphatase 1 (PP1), providing a possible link between the SIN cascade and cytoskeletal regulation during cytokinesis. Using these preliminary studies as a foundation, this application seeks to initiate an evaluation of the roles that Mob1 plays in coordinating mitosis and cytokinesis in mammalian cells. The lines of experimentation that form Specific Aim 1 of this application will characterize the localization dynamics of human Mob1 using co-localization studies and live cell imaging. Further, the role of Mob1 in the coordination of mitosis and cytokinesis will be assessed by disrupting Mob1 expression by siRNA knockdown, and analyzing Mob1-minus cells for mitotic defects. These efforts should build a strong foundation for future applications, and ultimately lead to a clearer understanding of how mitosis and cytokinesis is coordinated, and confirm whether the strategies employed by unicellular fungi to regulate septation are conserved in higher eukaryotes.