Minisatellite alterations in ZRT1 mutants occur via RAD52-dependent and RAD52-independent mechanisms in quiescent stationary phase yeast cells.

Abstract Alterations in minisatellite DNA repeat tracts are associated with a variety of human diseases including Type 1 diabetes, progressive myoclonus epilepsy, and some types of cancer. However, in spite of their role in human health, the factors required for minisatellite alterations are not well understood. We previously identified a stationary phase specific increase in minisatellite instability caused by mutations in the high affinity zinc transporter ZRT1 , using a minisatellite inserted into the ADE2 locus in Saccharomyces cerevisiae . Here, we examined ZRT1 -mediated minisatellite instability in yeast strains lacking key recombination genes to determine the mechanisms by which these alterations occur. Our analysis revealed that minisatellite alterations in a Δ zrt1 mutant occur by a combination of RAD52 -dependent and RAD52 -independent mechanisms. In this study, plasmid-based experiments demonstrate that ZRT1 -mediated minisatellite alterations occur independently of chromosomal context or adenine auxotrophy, and confirmed the stationary phase timing of the events. To further examine the stationary phase specificity of ZRT1 -mediated minisatellite alterations, we deleted ETR1 and POR1 , genes that were previously shown to differentially affect the viability of quiescent or nonquiescent cells in stationary phase populations. These experiments revealed that minisatellite alterations in Δ zrt1 mutants occur exclusively in quiescent stationary phase cells. Finally, we show that loss of ZRT1 stimulates alterations in a derivative of the human HRAS1 minisatellite. We propose that the mechanism of ZRT1 -mediated minisatellite instability during quiescence is relevant to human cells, and thus, human disease.