Live imaging system for visualizing nuclear pore complex (NPC) formation during interphase in mammalian cells.

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Nuclear pore complexes (NPCs) are crucial for nucleocytoplasmic transport, facilitating molecular exchange between the nucleus and cytoplasm.
• While NPC structure is well-defined, the mechanisms regulating NPC assembly and maintenance during interphase remain largely unknown.
• RCC1 (Regulator of Chromosome Condensation 1) is a guanine nucleotide exchange factor involved in various cellular processes.

Purpose of the Study:

• To investigate the role of RCC1 in nuclear pore complex (NPC) formation and maintenance during interphase in mammalian cells.
• To establish a live-cell system for observing NPC formation dynamics.
• To elucidate the relationship between RCC1 activity and NPC integrity.

Main Methods:

• Utilized the temperature-sensitive tsBN2 cell line, a mutant of baby hamster kidney 21 cells lacking functional RCC1 at restrictive temperatures.
• Developed a reversible system to control RCC1 activity by altering temperature, enabling dynamic observation of NPC formation.
• Analyzed the impact of RCC1 depletion on nucleoporin (Nup) levels and NPC structure.

Main Results:

• A lack of RCC1 activity significantly inhibited NPC formation during interphase.
• RanGTP, regulated by RCC1, was identified as a key factor required for NPC assembly in interphase mammalian cells.
• Reduced RCC1 activity led to a decrease in specific nucleoporins, particularly those with phenylalanine-glycine repeats, suggesting a role in maintaining NPC integrity.

Conclusions:

• RCC1 plays a critical role in the formation and maintenance of nuclear pore complexes during interphase.
• RanGTP signaling is essential for NPC assembly in mammalian cells.
• The findings provide new insights into the regulation of nucleocytoplasmic transport and NPC structure.