Transcriptional studies on yeast SEC genes provide no evidence for regulation at the transcriptional level

A number of proteins have been identified as components of the secretory pathway of Saccharomyces cerevisiae (SEC gene products). However, very little is known about the expression of these components and their regulation at the transcriptional level. In this study yeast cells were exposed to conditions that changed the secretory activity of the cells. The conditions analysed include the different stages of the cell cycle, overexpression of secretory proteins, and block of secretion and endocytosis. The effect of these conditions on the transcriptional expression levels of a number of SEC genes (SAR1, SEC1, SEC14, SEC17, SEC18, SEC23, SEC62, YPT1) was analysed. In summary, no major changes in transcriptional expression levels could be detected. From these results we conclude that the components of the secretory pathway are expressed constitutively and that no general regulation of transcription exists, that could adjust the expression level of the SEC genes to the secretory activity of the cells.