The RNA export factor Mex67 functions as a mobile nucleoporin.

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Messenger RNA (mRNA) export from the nucleus is vital for gene expression.
• The RNA export factor Mex67 is essential for mRNA transport via the nuclear pore complex (NPC) in yeast.
• The precise molecular mechanism of Mex67-mediated mRNA export remains unclear.

Purpose of the Study:

• To investigate the molecular mechanism by which Mex67 facilitates mRNA export.
• To elucidate the role of Mex67's interaction with mRNA and the NPC.
• To determine the functional localization of Mex67 during mRNA export.

Main Methods:

• Quantitative fluorescence microscopy in live budding yeast cells.
• Analysis of Mex67 localization and interaction with mRNA and NPC components.
• Functional complementation assays using Mex67-Nup116 fusion protein.

Main Results:

• Mex67 shows minimal interaction with mRNA in the nucleus and localizes to the NPC independently of mRNA.
• Mex67 binds to FG repeats within the NPC, and this interaction is unaffected by the ATPase Dbp5.
• The essential function of Mex67 is localized to the NPC, as demonstrated by rescuing a MEX67 deletion with a Mex67-Nup116 fusion.

Conclusions:

• Mex67 functions as a mobile component of the NPC.
• Mex67 receives mRNA export substrates within the NPC's central channel.
• This mechanism facilitates the translocation of mRNA from the nucleus to the cytoplasm.