Post-translational modifications in mitotic yeast cells

Authors


Correspondence to L. T. Nevalainen, Institute of Biotechnology, University of Helsinki, Valimotie 7, SF-00380 Helsinki, Finland

Abstract

We have recently shown that secretion of invertase is not inhibited in the yeast Saccharomyces cerevisiae during mitosis, but continues, as during interphase. This is in contrast with the mammalian cell, where membrane traffic stops at the onset of prometaphase. Here we extend our findings by showing that the bulk of the cell surface glycoproteins and mannans, as well as the yeast pheromone α-factor, traverse the sccretory pathway during mitosis. We show that the mitotic cells are able to carry out several types of post-translational modification of secretory proteins. (a) The secretory protein invertase was oligomerized and extensively glycosylated, (b) the N-glycan cores of bulk-cell surface mannans were extended with outer chains, (c) some N-glycans were phosphorylated, (d) the protein-bound O-glycans were extended up to tetramannosides, (e) prepro-ka-factor was proteolytically processed to α-factor molecules. We conclude that the secretory pathway in yeast remains fully functional throughout the cell cycle.

Abbreviations
TLC

high performance thin-layer chromatography

ER

endoplasmic reticulum

Man

mannose

GlcNAc

N-acetyl glucosamine