A temperature-sensitive NUP116 null mutant forms a nuclear envelope seal over the yeast nuclear pore complex thereby blocking nucleocytoplasmic traffic

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The nuclear pore complex (NPC) regulates transport between the nucleus and cytoplasm.
• NUP116 is a component of the yeast NPC, not essential for viability but affects growth at different temperatures.

Purpose of the Study:

• To investigate the cellular and ultrastructural consequences of NUP116 deletion in yeast.
• To elucidate the mechanism by which NUP116 deficiency impacts nuclear transport.

Main Methods:

• Yeast genetics (NUP116 deletion).
• Electron microscopy for nuclear envelope morphology.
• In situ hybridization with poly(dT) probes for RNA localization.

Main Results:

• NUP116 deletion leads to the formation of double membrane seals over NPCs at the cytoplasmic face.
• Accumulation of electron-dense material and nuclear envelope herniations around NPCs were observed.
• Polyadenylated RNA accumulated within the nucleus, suggesting blocked export.

Conclusions:

• The NUP116 protein is crucial for maintaining nuclear envelope integrity and nucleocytoplasmic transport.
• NPCs lacking NUP116 may remain export-competent, but membrane sealing obstructs traffic.
• This defect leads to nuclear accumulation of RNA and is lethal at elevated temperatures.