Over-Expression of YLR162W in Saccharomyces cerevisiae Inhibits Cell Proliferation and Renders Cells Susceptible to the Hypoxic Conditions Induced by Cobalt Chloride

Abstract

YLR162W is an uncharacterized Saccharomyces cerevisiae ORF whose transcript level is elevated in cells under environmental stress, during α-factor response and in stationary phase. We obtained a partial cDNA clone of YLR162W by subtractive hybridization cloning of genes that were not expressed in a CoCl₂ resistant DNA synthesis mutant but expressed in its wild type counterpart. Our studies demonstrated that YLR162W transcript level was reduced in BY4741 cells upon exposure to the hypoxia mimetic agent CoCl₂, and continuous expression of full length YLR162W from a plasmid borne copy of the gene rendered BY4741 cells extremely susceptible to the hypoxic conditions induced by CoCl₂. At initial time points following the induction of YLR162W expression, cell cycle progression was inhibited with the emergence of a distinct sub-G1 peak indicative of apoptotic cells, mitochondrial membrane potential was also decreased along with an increase in the fraction of cells permeable to propidium iodide; none of the above was further affected by CoCl₂. The up-regulation of Ylr162wp in cells exposed to environmental stress and in non-replicating cells appears to be related to its growth inhibitory properties presented in this report.