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Updated: Aug 10, 2026

G2-seq: A High Throughput Sequencing-based Technique for Identifying Late Replicating Regions of the Genome
Published on: March 22, 2018
The origin recognition complex, SIR1, and the S phase requirement for silencing
C A Fox1, A E Ehrenhofer-Murray, S Loo
1Department of Molecular and Cell Biology, Division of Genetics, 401 Barker Hall, University of California, Berkeley, CA 94720, USA.
Transcription silencing in Saccharomyces cerevisiae involves DNA replication. The origin recognition complex (ORC) and S phase passage are crucial for silencing, with roles separable from replication initiation.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Transcription silencing in Saccharomyces cerevisiae is linked to DNA replication.
- The origin recognition complex (ORC) plays a role in both DNA replication initiation and transcriptional silencing.
- Establishment of silencing at HML and HMR loci requires passage through S phase.
Purpose of the Study:
- To investigate the relationship between DNA replication and transcriptional silencing in Saccharomyces cerevisiae.
- To determine the specific roles of ORC and S phase in silencing at HML and HMR loci.
- To differentiate the functions of ORC in replication initiation versus transcriptional silencing.
Main Methods:
- Investigating the requirement of S phase passage for HMR silencing under conditions where ORC is not required.
- Examining the effect of tethering Sir1 protein to the HMR-E silencer on ORC-dependent silencing.
- Assessing the Sir1-independent role of ORC in telomeric transcriptional silencing.
Main Results:
- Passage through S phase is necessary for HMR silencing, independently of ORC's role in replication initiation.
- The requirement for ORC in HMR silencing can be bypassed by tethering Sir1 to the HMR-E silencer.
- ORC has a distinct, Sir1-independent role in telomeric transcriptional silencing.
Conclusions:
- The role of ORC in transcriptional silencing is separable from its function in DNA replication initiation.
- S phase passage is essential for silencing, independent of replication initiation at silencers.
- These findings elucidate distinct mechanisms by which DNA replication processes influence gene silencing.
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