This project is aimed at investigating a number of key aspects of the production and recovery of foreign proteins from Saccharomyces cerevisiae, where gaps in basic knowledge are limiting the effectiveness of the yeast as a production host for biotechnology.
The baking and brewing yeast Saccharomyces cerevisiae (S cerevisiae) is a single celled organism that has the same basic cellular organization and processes as higher eukaryotic organisms including humans. It is also the most highly characterized eukaryote and is easy to cultivate and harmless. These features make S cerevisiae an ideal host for the biotechnological production of products normally synthesized by less amenable higher cells. Many examples now exist that show the huge potential of yeast in the production of hormones, recombinant vaccines, and blood proteins. Initial levels of production of foreign proteins in yeast have been variable and often disappointing reflecting gaps in basic knowledge of the processes involved in protein biosynthesis and recovery. This project is aimed at such key areas. Results have extended the capability of yeast for the primary production of proteins and their recovery via secretion from the cell and, in the case of non-secretable proteins, cell autolysis.
Current objectives are in studies relating to the production of heterologous proteins in yeast, the recovery of heterologous proteins by secretion, and the recovery of heterologous proteins by cell lysis.
Significant results of work to date are the excellent performance of the HSP12 promoter in producing high yields of recombinant trout growth hormone, a biotech product;
The successful isolation of new mutant yeast strains showing enhanced levels of heterologous protein secretion. These are of biotechnological significance as they increase product yield by many fold and in addition, genetically mark bottlenecks in the expression secretion process;
The possibility of controlling yeast cell wall dynamics by manipulating genes which influence the stability of this structure has been demonstrated extending the usefulness of yeast as a host for biotechnological production. In addition the isolation of new mutants affecting cell wall dynamics identifies further gene funct ions that may be manipulated to improve the efficiency of heterologous protein recovery from yeast.
Saccharomyces cerevisiae is a major host for the production of biotechnologically-important proteins. One reason for this is its long association with the food and drink industry,and the great potential of genetically modifying industrial yeasts to fulfil these traditional fermentation roles more effectively. S.cerevisiae was also early recognised as an important host for producing cloned gene products for the pharmaceutical industry. One reason is that,as a eukaryote,it provides post-translational modifications like mammalian cells (protein folding,acetylation,glycosylation at the same sites. Another is the ability to secrete proteins,which,since yeast does not normally secrete many proteins, provides an instantaneous semi-purification of the heterologous product. Despite advanced characterization, S.cerevisiae still has many gaps in basic understanding. It is the purpose of this proposal to address some of these deficiencies, and, in so doing, enhance the capability of the yeast to fulfil its role as a host for the production of biotechnologically important proteins. Studies on the production of heterologous proteins will involve novel promoters with particular expression characteristics,high stability multi-copy vectors and reporter gene mRNAs which can be translated with high efficiency. Secretion studies address problems associated with very high expression of secreted proteins and the isolation of mutants showing improved secretion capabilities. Studies off cell wall dynamics relate to the release of periplasmically located secreted proteins and,as a new capability,the release of cytoplasmically expressed proteins via autolysis,due to induced weakening of the normally strong ,breakage-resistant cell wall. The latter provide .....
Funding SchemeCSC - Cost-sharing contracts
LU1 3ET Luton
SW1P 3JF London