A glutamine/asparagine-rich fragment of Gln3, but not the full-length protein, aggregates in Saccharomyces cerevisiae

Abstract

The amino acid sequence of protein Gln3 in yeast Saccharomyces cerevisiae has a region enriched with Gln (Q) and Asn (N) residues. In this study, we analyzed the effects of overexpression of Gln3 and its Q/N-rich fragment fused with yellow fluorescent protein (YFP). Being overexpressed, full-length Gln3-YFP does not form aggregates, inhibits vegetative growth, and demonstrates nuclear localization, while the Q/N-rich fragment (Gln3QN) fused with YFP forms aggregates that do not colocalize with the nucleus and do not affect growth of the cells. Although detergent-resistant aggregates of Gln3QN are formed in the absence of yeast prions, the aggregation of Gln3QN significantly increases in the presence of [PIN⁺] prion, while in the presence of two prions, [PSI⁺] and [PIN⁺], the percentage of cells with Gln3QN aggregates is significantly lower than in the strain bearing only [PIN⁺]. Data on colocalization demonstrate that this effect is mediated by interaction between Gln3QN aggregates and [PSI⁺] and [PIN⁺] prions.