1. The function of the molecular chaperone Hsp90.

Heat shock protein 90 (Hsp90) is an ATP dependant molecular chaperone essential for both creating and maintaining the active conformation of key regulatory proteins, such as certain hormone receptors, mitogen activated protein kinases and tumour suppressors such as p53 and Rb. In order to achieve its function, Hsp90 acts as the centre of a multi-protein chaperosome complex that includes an array of co-chaperones. The chaperosome complex has been highly conserved throughout the eukaryotic lineage, and we exploit yeast as a genetically tractable model system in which to investigate the contribution made by each co-chaperone to the overall function of the chaperosome. For example, we can assess activity of Hsp90 substrates - such as the glucocorticoid receptor and the pp60v-src oncogernic kinase - in genetic backgrounds deleted for the genes encoding the co-chaperones.

2. The role played by the Smc5/6 complex in maintenance of genome integrity

There are three Structural Maintenance of Chromosomes complexes. The core of all three is composed of a heterodimer. One complex, cohesin (Smc1/3), keeps sister chromatids together prior to mitosis. Condensin (Smc2/4), is responsible for the chromosome condensation that occurs during mitosis. The third, Smc5/6, has an essential yet poorly characterised role. We are trying to understand the role played by this complex in maintaining genome integrity. Smc5/6 is found in a complex containing at least five other proteins, Nse1-5 (Non Smc Elements). We are generating mutant alleles of the corresponding genes, in order to observe how they disturb genome structure, thereby generating insight into the function of the Smc5/6 complex itself.

3. Conditional mutants in QRI2/NSE4 arrest at the G2/M transition.

Cells deleted for NSE4 bearing a vector-borne wild type allele (W+), or the nse4-4ts allele, were grown at 250C and shifted to 370C for 4 hours. Cells were fixed, followed by staining DNA and spindles with DAPI (B), and anti-tubulin (C), respectively. Panels A (phase), B & C are cells from the same field of view. FACS analysis reveals that cells.