Permeability measurements with closed vesicles from rat liver nuclear envelopes

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• The nuclear envelope regulates molecular traffic between the nucleus and cytoplasm.
• Understanding nuclear transport mechanisms is crucial for cellular function and disease research.

Purpose of the Study:

• To investigate the transport properties of proteins and nucleic acids across isolated nuclear envelopes.
• To elucidate the role of specific molecules like histones, RNA species, and nucleotides in nuclear transport.

Main Methods:

• Preparation of closed nuclear envelope ghosts from rat liver nuclei.
• Transport measurements of various proteins (histones, non-nuclear proteins) and nucleic acids (poly(A)-containing RNA, mRNA, rRNA).
• Utilized Triton X-100 treatment and comparative studies with open vesicles to exclude adsorption effects; assessed nucleotide (GTP, GDP, ATP) influence on transport.

Main Results:

• Histones rapidly accumulated in nuclear envelope ghosts, unlike other proteins.
• Guanosine triphosphate (GTP) and guanosine diphosphate (GDP) significantly inhibited histone exchange across the nuclear envelope.
• Adenosine triphosphate (ATP) at 2 mM enhanced the complete export of poly(A)-containing RNA from vesicles.
• Poly(A)-containing RNA and poly(A) were transported unidirectionally.

Conclusions:

• The nuclear envelope possesses distinct transport mechanisms for proteins and RNA.
• Nucleotide triphosphates play regulatory roles in nuclear transport, with ATP specifically promoting poly(A)-containing RNA export.
• Isolated nuclear envelope vesicles serve as a valuable model for studying directional nucleocytoplasmic transport pathways.