Regulation of heterologous protein production in relation to cell growth

Background.

Secretion of proteins from yeast cell is complex and rate-limiting. The secretion rate of heterologous proteins expressed in yeasts correlates with the specific growth rate and cell cycle progression of the cells. However, as cell cycle and growth rate correlate as well, it is not established which of these processes controls protein secretion.

Aims and methods.

The research question of this project is whether protein secretion in yeasts (with focus on Pichia pastoris) is regulated by the specific growth rate or by the cell cycle stage of the cells. P. pastoris cells expressing a heterologous protein will be cultivated under tightly controlled (chemostat) conditions at different specific growth rates. Specific productivity will be correlated to specific growth rates and cell cycle phase distribution. Transcriptome analyses will allow to identify genes which are co-regulated with protein secretion.

In a second setup, cell samples of a low and a high growth rate setpoint will be separated for their cell cycle phase by FACS, and subjected to transcriptomics. This approach will allow for the differentiation between growth rate dependent and cell cycle dependent gene regulation.

The identified gene regulation patterns will be subjected to the identification of regulatory DNA motifs using bioinformatics tools which will be developed in parallel under supervision of David KREIL. Putative DNA motifs will then be further characterized.