Structural and functional analysis of mRNA export regulation by the nuclear pore complex

Area of Science:

• Molecular Biology
• Cell Biology
• Structural Biology

Background:

• The nuclear pore complex (NPC) regulates nucleocytoplasmic transport.
• The precise role of the NPC in macromolecular transport, particularly mRNA export, requires further elucidation.
• DEAD-box helicase DDX19, along with nucleoporins Gle1, Nup214, and Nup42, is crucial for the final step of mRNA export.

Purpose of the Study:

• To elucidate the structural basis of DDX19 activation by Gle1 and Nup42 during mRNA export.
• To investigate the evolutionary conservation of the Gle1-Nup42 interaction.
• To determine the role of Gle1 stability in DDX19 activation and its link to motor neuron diseases.

Main Methods:

• X-ray crystallography to determine the structures of Gle1•Nup42 and Gle1•Nup42•DDX19 complexes.
• Biochemical reconstitution of the DDX19 ATPase cycle.
• Analysis of mutation effects on Gle1 thermostability.

Main Results:

• Crystal structures reveal an evolutionarily conserved binding mode between Gle1 and Nup42 across three organisms.
• Human DDX19 activation by Gle1 does not require IP6, differing from fungal homologs.
• Gle1 stability is critical for DDX19 activation; mutations associated with motor neuron diseases reduce Gle1 thermostability.
• Structures show DDX19 transitioning from an auto-inhibited to an RNA-binding competent state upon complex formation.

Conclusions:

• The findings provide a structural foundation for understanding the mechanism of mRNA export in humans.
• Nucleoporin misfolding, indicated by decreased Gle1 thermostability, is implicated as a determinant in motor neuron diseases.
• This study advances the mechanistic understanding of how the nuclear pore complex facilitates macromolecular transport.