The role of promoter elements of a ribosomal protein gene in Saccharomyces cerevisiae under various physiological conditions.

Previous work in our laboratory has shown that the 5' nontranscribed promoter region of the gene for ribosomal protein (rp) S16A-1 of Saccharomyces cerevisiae, when fused to a lacZ gene, is necessary and sufficient to cause an increase in expression of the heterologous lacZ gene fusion product after cells have been shifted from a glycerol to glucose carbon source. This increase in expression is characteristic of that observed with the native rp gene. We have sought to define more precisely those areas of the promoter that may be involved in the differential expression/regulation of RPS16A-1 when host cells are subjected to a variety of nutritional environments. It has already been demonstrated by others that the promoter regions of most rp genes contain at least one consensus element, designated UASrpg, which is necessary for the transcriptional activation and maintenance of expression of the gene during steady-state growth in rich media. Our main experimental approach has been to create a series of 5' end deletions in the promoter region of RPS16A-1. The individual truncated promoter fragments were then ligated to a lacZ fusion reporter construct. By assaying the cells for production of beta-galactosidase and determining the abundance of lacZ mRNA, we have been able to determined the extent of fusion product expression. We assayed cells under three physiological conditions: steady-state growth in glucose, steady-state growth in glycerol and during sporulation. We report four main findings of our work.