MANNOSYLPHOSPHATE TRANSFER TO CELL-WALL MANNAN IS REGULATED BY THE TRANSCRIPTIONAL LEVEL OF THE MNN4 GENE IN SACCHAROMYCES-CEREVISIAE

Mannosylphosphorylation is a major oligosaccharide modification that p rovides negative charge in the Saccharomyces cerevisiae cell wall, Alt hough two genes, MNN6 and MNN4, which encode a mannosylphosphate trans ferase and its putative positive regulator, respectively, are involved in this modification, the amount of Mnn4p has been found to be a limi ting factor for mannosylphosphorylation. The level of mannosylphosphor ylation increased at late-logarithmic and stationary phases of cell gr owth, and this was correlated to the transcriptional enhancement of MN N4. We also find that mannosylphosphate transfer to mannan is negative ly regulated by the protein kinase A pathway, while the presence of 0. 5 M potassium chloride enhanced MNN4 transcription, This type of trans criptional regulation is observed in many stress response genes, imply ing that mannosylphosphate transfer is involved in the cellular respon se to a variety of stresses. (C) 1997 Federation of European Biochemic al Societies.