Gle2p is essential to induce adaptation of the export of bulk poly(A)+ mRNA to heat shock in Saccharomyces cerevisiae

The export of bulk poly(A)(+) mRNA is blocked under heat-shocked (42degreesC) conditions in Saccharomyces cerevisiae. We found that an mRNA export factor Gle2p rapidly dissociated from the nuclear envelope and diffused into the cytoplasm at 42degreesC. However, in exponential phase cells pretreated with mild heat stress (37degreesC for 1 h), Gle2p did not dissociate at 42degreesC, and the export of bulk poly(A)(+) mRNA continued. Cells in stationary phase also continued with the export of bulk poly(A)(+) mRNA at 42degreesC without the dissociation of Gle2p from the nuclear envelope. The dissociation of Gle2p was caused by increased membrane fluidity and correlated closely with blocking of the export of bulk poly(A)(+) mRNA. Furthermore, the mutants gle2Delta and rip1Delta could not induce such an adaptation of the export of bulk poly(A)(+) mRNA to heat shock. Our findings indicate that Gle2p plays a crucial role in mRNA export especially under heat-shocked conditions. Our findings also indicate that the nuclear pore complexes that Gle2p constitutes need to be stabilized for the adaptation and that the increased membrane integrity caused by treatment with mild heat stress or by survival in stationary phase is likely to contribute to the stabilization of the association between Gle2p and the nuclear pore complexes.