Identification and characterization of an actomyosin contractile ring involved in S. cerevisiae cytokinesis

The cell cycle culminates with the fundamental cellular process known as cytokinesis. There are many important regulatory aspects involved in cytokinesis which insure the integrity and viability of both the mother and daughter cell. Our understanding of the process of cytokinesis and the many aspects surrounding this process has been relatively slow to emerge. This is partially due to a lack of model organisms amenable to powerful genetic analyses.;Using this model system, we have identified and analyzed new contractile ring proteins. This has led to a higher understanding of actomyosin ring organization. Studying the dynamic relationship between a subset of proteins involved in cytokinesis allowed the generation of a novel model which hypothesizes that a non-contractile group of proteins at the bud neck actually trigger actomyosin ring contraction. Finally, we have discovered a link between cytokinesis and another important aspect of the cell cycle; nuclear envelope fission.;In animal cells cytokinesis is mediated by an actomyosin contractile ring which appears to pull the plasma membrane inward, eventually resulting in two distinct cells. This thesis describes the identification of an actomyosin ring in the budding yeast, Saccharomyces cerevisiae. This discovery has opened the door to use budding yeast as a model system to dissect the processes involved in actomyosin ring based cytokinesis.