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Nucleoplasmin uptake by facilitated transport and intranuclear binding
I Vancurova1, W Lou, T M Paine
1Department of Biological Sciences, St. John's University, Jamaica, NY 11439.
European Journal of Cell Biology
|October 1, 1993
Summary
Researchers developed a novel method to study nuclear transport. They found that nucleoplasmin enters the nucleus via facilitated transport and accumulates due to binding, both processes requiring ATP.
Area of Science:
- Cell Biology
- Molecular Mechanisms
- Eukaryotic Transport
Background:
- Nuclear protein translocation is crucial for eukaryotic cells.
- The precise molecular mechanisms of nuclear transport and accumulation are not fully understood.
Purpose of the Study:
- To investigate the mechanisms of protein translocation and accumulation into the cell nucleus.
- To elucidate the transport mechanism of nucleoplasmin (Np).
Main Methods:
- Developed a novel experimental system using isolated oocyte nuclei and conjoined transport pairs.
- Monitored nuclear envelope integrity and quantified transportant protein distribution over time.
- Assessed concentration gradients versus chemical activity gradients by puncturing the nuclear envelope.
Main Results:
- Demonstrated that nucleoplasmin (Np) undergoes facilitated transport through the nuclear pore complex, not active transport.
- Showed that Np's high nuclear accumulation is due to subsequent intranuclear binding.
- Confirmed that both facilitated transport and intranuclear binding are ATP-dependent.
Conclusions:
- The study reveals a dual mechanism for nuclear protein accumulation: facilitated transport followed by binding.
- Intranuclear binding, requiring cytoplasmic factors, is key to achieving high nuclear concentrations of proteins like Np.
- The findings provide critical insights into fundamental eukaryotic nuclear transport processes.