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A role for a replicator dominance mechanism in silencing
1Department of Biomolecular Chemistry, 587 MSC 1300 University Avenue, University of Wisconsin, Madison, WI 53706-1532, USA.
The EMBO Journal
|July 7, 1999
Summary
The origin recognition complex (ORC) plays a dual role in DNA replication and silencing. ORC binding to the HMR-E silencer site is crucial for silencing but not initiation, revealing nearby replicators that impact silencing efficiency.
Area of Science:
- Molecular Biology
- Genetics
- Chromatin Biology
Background:
- The HMR-E locus is a key region for studying gene silencing in yeast.
- The Origin Recognition Complex (ORC) is essential for DNA replication initiation and has roles in transcriptional regulation.
Purpose of the Study:
- To investigate the function of the natural HMR-E silencer in regulating replication initiation and silencing by ORC.
- To determine the interplay between ORC binding sites and the activity of nearby replicators.
Main Methods:
- Analysis of HMR-E function in the presence of the silencer.
- Investigating replication initiation and silencing in orc2-1 mutant strains.
- Deletion analysis of sequences flanking HMR-E.
Main Results:
- The ORC-binding site (ACS) of HMR-E is essential for silencing but not replication initiation.
- Proximity to HMR-E, non-silencer replicators were identified that are sensitive to ORC defects.
- Inactivation of these nearby replicators enhanced silencing, suggesting a suppressive role for ORC at the HMR-E ACS.
Conclusions:
- ORC bound to the HMR-E silencer ACS suppresses the activity of neighboring ORC molecules, thereby promoting silencing.
- Differences in ORC-binding site organization within HMR significantly impact ORC function.
- Inefficient replication initiation at HMR-E suggests that closely spaced replicators inhibit initiation.