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Updated: Jul 28, 2026
07:47
Microscopy of Fission Yeast Sexual Lifecycle
Published on: March 9, 2016
Chromatin boundaries in budding yeast: the nuclear pore connection
Kojiro Ishii1, Ghislaine Arib, Clayton Lin
1Departments of Biochemistry and Molecular Biology, University of Geneva, 30, Quai Ernest-Ansermet, Geneva, Switzerland.
Cell
|June 14, 2002
Summary
Nuclear transport proteins act as chromatin boundary elements in yeast, tethering genes to the nuclear pore complex to prevent heterochromatin spread and maintain gene expression.
Area of Science:
- Molecular Biology
- Epigenetics
- Yeast Genetics
Background:
- Chromatin boundary activities (BAs) define regions that insulate genes from silencing.
- The silent mating-type locus HML in Saccharomyces cerevisiae is a model for studying heterochromatin formation and boundary elements.
- Proteins involved in nuclear transport are increasingly recognized for roles beyond their canonical functions.
Purpose of the Study:
- To identify and characterize novel chromatin boundary activities in Saccharomyces cerevisiae.
- To investigate the role of nuclear-cytoplasmic transport proteins in epigenetic regulation.
- To elucidate the mechanism by which transport proteins establish boundary activities at the HML locus.
Main Methods:
- Genetic screening to identify boundary activities.
- Immunolocalization and live-cell imaging to track protein localization.
- Chromatin immunoprecipitation (ChIP) to assess DNA-protein interactions.
- Genetic manipulation including gene deletion and targeted DNA element modification.
Main Results:
- Several nuclear-cytoplasmic transport proteins, including exportins Cse1p, Mex67p, and Los1p, exhibit chromatin boundary activity.
- These transport proteins physically tether the HML locus to the Nup2p receptor at the nuclear pore complex (NPC).
- Deletion of NUP2 eliminates the boundary activity of these transport proteins, while targeted tethering to DNA restores it.
Conclusions:
- Physical tethering of genomic loci to the NPC by nuclear transport proteins can establish chromatin boundaries.
- This mechanism prevents the spread of heterochromatin, thereby maintaining an active transcriptional state.
- Nuclear pore complex components play a direct role in epigenetic regulation of gene expression.
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