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Ran binds to chromatin by two distinct mechanisms
Daniel Bilbao-Cortés1, Martin Hetzer, Gernot Längst
1European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
Current Biology : CB
|July 18, 2002
Summary
Ran GTPase binds directly to chromatin, influencing spindle and nuclear envelope assembly during cell division. This chromatin binding capacity is key for localized mitotic processes.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Ran GTPase is crucial for nucleocytoplasmic transport and mitotic events like spindle formation and nuclear envelope (NE) assembly.
- High local concentrations of GTP-bound Ran near mitotic chromatin are essential for these functions.
- Previous models suggested RanGTP localization relies solely on its exchange factor, RCC1, binding to chromatin.
Purpose of the Study:
- To investigate the direct binding of Ran to chromatin.
- To determine the role of RCC1 in Ran's chromatin association.
- To elucidate how Ran binding to chromatin influences NE membrane association and mitotic processes.
Main Methods:
- Chromatin binding assays to assess Ran-chromatin interactions.
- Experiments to differentiate RCC1-dependent and -independent Ran binding.
- Analysis of NE membrane affinity in the presence of chromatin-bound Ran.
Main Results:
- Ran was shown to bind directly to chromatin through two distinct modes: one dependent on RCC1 and another independent of it.
- Chromatin-bound Ran enhances the affinity of chromatin for nuclear envelope membranes.
- These findings reveal a novel mechanism for Ran's role in mitosis.
Conclusions:
- Chromatin possesses an intrinsic Ran binding capacity, independent of RCC1.
- This Ran binding capacity of chromatin is a significant contributor to the localized assembly of the spindle and NE during mitosis.
- The study reframes the understanding of Ran's function in cell division.