A genetic approach to study polyubiquitination in Saccharomyces cerevisiae

Ubiquitin has seven lysines, all of which are used to generate polyubiquitin chains in the yeast Saccharomyces cerevisiae. While the biology associated with chains formed through lysines 48 and 63 is well studied, other chain types are more poorly characterized. We outline a methodology for using synthetic genetic analysis to examine ubiquitin mutants. Ubiquitin is encoded by four loci, necessitating several alterations to standard protocols, including the use of the SK1 strain background, which sporulates with very high efficiency. The methods described here could be used to examine other ubiquitin mutants, including those that do not support viability.