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Published on: March 22, 2018
DNA replication-independent silencing in S. cerevisiae
1Division of Genetics and Development, Department of Molecular and Cell Biology, University of California, 401 Barker Hall, Berkeley, CA 94720, USA.
Science (New York, N.Y.)
|February 7, 2001
Summary
DNA replication is not required for silencing of mating-type loci in Saccharomyces cerevisiae. Heterochromatin formation and silencing occur independently of the replication fork
Area of Science:
- Molecular Biology
- Yeast Genetics
- Epigenetics
Background:
- Silent mating loci in Saccharomyces cerevisiae are repressed via heterochromatin formation.
- Heterochromatin assembly requires a cell cycle event between early S phase and G(2)/M phase.
- DNA replication has been the assumed trigger for this cell cycle-dependent silencing.
Purpose of the Study:
- To investigate whether DNA replication through the silent mating-type locus HMRa is essential for establishing heterochromatin-mediated silencing.
- To differentiate the role of DNA replication from other cell cycle events in silencing establishment.
Main Methods:
- Monitoring heterochromatin formation at the chromosomal HMRa locus.
- Monitoring heterochromatin formation at a nonreplicating extrachromosomal HMRa cassette.
- Analyzing silencing establishment as cells progressed through S phase.
Main Results:
- Silencing was established with equal efficiency at both the chromosomal and extrachromosomal HMRa loci.
- Heterochromatin formation and silencing occurred independently of DNA replication fork passage through the HMR locus.
- Silencing establishment retained a cell cycle dependence, despite the absence of replication.
Conclusions:
- The prevailing assumption that DNA replication is required for mating-loci silencing in yeast is incorrect.
- Cell cycle-dependent silencing establishment can occur without passage of the replication fork through the target locus.
- Other cell cycle events, not DNA replication itself, likely regulate the timing of heterochromatin formation and silencing.
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