The laboratory is focused on the study of the genetics, biochemistry and cell biology of yeast cell cycle control and DNA repair. These are exciting and competitive areas of research with important implications for the understanding of carcinogenesis. The ability to apply rigorous yet simple genetic techniques to the study of these processes in yeast has meant that they have proven to be invaluable experimental model systems. There are currently two major projects in the laboratory which are outlined below.
We have recently isolated a temperature sensitive mutation which blocks one of the final steps in cell division, cytokinesis. Cytokinesis requires the regulated assembly and subsequent contraction of an actomyosin ring structure at the site of cell division, the mother/bud neck. We are currently characterizing high dosage suppressors of this mutation with the aim of identifying further components of the contractile ring. The long term goals of the work are to describe the order of assembly of the structure and the precise protein/protein interactions which dictate this process. The co-ordination of cytokinesis with mitosis and the initiation of ring contraction is a second important but as yet poorly understood aspect of cell cycle control that we are actively investigating.
In the same genetic screen which identified the cytokinesis mutation we have identified two further mutants which restore viability to a checkpoint deficient allele the rad4 gene in the presence of hydroxyurea, an inhibitor of DNA replication. These mutations also restore resistance to UV irradiation mediated DNA damage in the presence of the rad4 mutation. The Characterisation of these mutants is at a very preliminary stage but the project(s) would require basic molecular genetic analysis of plasmid suppressors and detailed phenotypic analysis of the mutations in both the presence and absence of the conditional rad4 mutation.
During cell growth and division, genomic integrity is maintained by cellular surveillance mechanisms which have been termed DNA structure checkpoint controls. As well as ensuring that the events of the cell cycle occur in the correct order, these control mechanisms act to block cell cycle progression in response to both DNA damage and the inhibition of DNA replication. Checkpoint controls can be thought of as signal transduction pathways and loss of function often results in the development of cancer in man. Genetic and biochemical approaches in fission yeast have provided vital insights into the identity and function of checkpoint pathway proteins. Our interest centres on the role of rad4+/cut5.+ A gene which is essential for both DNA replication and DNA structure checkpoint function. Our current work is directed toward understanding the position at which the Cut5 protein acts within the checkpoint signaling cascade and its direct interactions with other checkpoint proteins; in particular the so called checkpoint Rad proteins.