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GAS3 , a developmentally regulated gene, encodes a highly mannosylated and inactive protein of the Gas family of Saccharomyces cerevisiae
Author(s) -
Rolli Eleonora,
Ragni Enrico,
RodriguezPeña José Manuel,
Arroyo Javier,
Popolo Laura
Publication year - 2010
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/yea.1788
Subject(s) - biology , saccharomyces cerevisiae , mutant , gene , gene family , biochemistry , gene expression , microbiology and biotechnology
The multigene GAS family of Saccharomyces cerevisiae is constituted by five genes encoding GPI‐anchored proteins required for cell wall or spore wall assembly. GAS1 and GAS5 are expressed in vegetative growth and repressed during sporulation, whereas GAS2 and GAS4 exhibit the opposite expression pattern. This study focuses on GAS3 , a still poorly characterized member of the family. To date, attempts to reveal the glucan elongase activity typical of Gas proteins have been unsuccessful, suggesting that Gas3p is the only inactive member of the family. Here, we compared the mRNA levels of GAS1, GAS3 and GAS5 and demonstrate that GAS3 is the weakest‐expressed paralogue in vegetative growth. Moreover, GAS3 mRNA increased during sporulation, showing a bimodal profile typical of the early–middle meiotic genes. GAS3 product was identified as a low‐abundance, polydisperse mannoprotein. Loss of Gas3p did not affect growth and sporulation. The overexpression of GAS3, driven by the GAS1 promoter, slightly reduced growth rate in a wild‐type strain and led to hyperaccumulation of Gas3p in the membranes and in the cell wall. To determine whether GAS3 could replace GAS1 function in vivo, GAS3 was also overexpressed in a gas1 Δ mutant. Increased amounts of Gas3p were not only unable to complement the defects of the gas1 Δ cells but exacerbated them. A mutated Gas3p–E283Q, where one of the catalytic glutamate residues essential for GH72 enzyme activity was replaced by glutamine, was also noxious to gas1 Δ cells, indicating that the increased expression of Gas3p, rather than a potential activity, is deleterious for gas1 Δ cells. Copyright © 2010 John Wiley & Sons, Ltd.