An RNA-export mediator with an essential nuclear export signal

Area of Science:

• Molecular Biology
• Cell Biology
• Virology

Background:

• The Rev protein of human immunodeficiency virus type 1 (HIV-1) is crucial for transporting viral messenger RNAs from the nucleus to the cytoplasm.
• In yeast, Rev facilitates the nuclear export of specific RNAs, relying on a nuclear export signal (NES) and interaction with the cellular cofactor Rip1.
• The existence of endogenous RNA export mediators interacting with Rip1 and possessing NESs is hypothesized but not yet confirmed.

Purpose of the Study:

• To identify and characterize novel cellular factors involved in nuclear RNA export in yeast.
• To investigate the role of a newly identified yeast protein, Gle1, in the context of RNA export pathways.
• To explore the potential functional mimicry between Gle1 and the HIV-1 Rev protein.

Main Methods:

• Characterization of a novel yeast protein, Gle1, including its molecular mass and functional domains.
• Site-directed mutagenesis of the identified nuclear export signal (NES) within Gle1.
• Analysis of RNA export efficiency in yeast strains with mutated Gle1.
• Biochemical assays to determine interactions between Gle1, Rip1, and Nup100.
• Subcellular localization studies of Gle1 within yeast cells.

Main Results:

• A new essential yeast protein, Gle1 (62,000 molecular mass), was identified and found to contain a functional NES.
• Mutation of Gle1's NES abolished the export of polyadenylated RNA from the nucleus.
• Gle1 was shown to interact with both the cellular cofactor Rip1 and the nucleoporin Nup100.
• Gle1 is predominantly localized at the nuclear pore complexes.

Conclusions:

• Gle1 is identified as a critical RNA export factor in yeast, essential for nuclear-cytoplasmic RNA translocation.
• Gle1's interaction profile and localization suggest a direct role in navigating the nuclear pore complex.
• These findings propose that the HIV-1 Rev protein may achieve viral RNA export by mimicking the essential cellular function of Gle1.