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An ARS element inhibits DNA replication through a SIR2-dependent mechanism
Amber Crampton1, FuJung Chang, Donald L Pappas
1Laboratory of Chromosome Replication, Van Andel Research Institute, Grand Rapids, MI 49503, USA.
Molecular Cell
|April 29, 2008
Summary
Sir2p histone deacetylase inhibits DNA replication by interacting with an inhibitory sequence (I(S)) at specific origins. This interaction promotes an unfavorable chromatin structure, preventing prereplicative complex assembly and DNA synthesis.
Area of Science:
- Molecular Biology
- Genetics
- Chromatin Biology
Background:
- DNA replication initiates at origins where prereplicative complexes (pre-RCs) assemble during G1 phase.
- Sir2p, a histone deacetylase, is known to regulate gene silencing and chromatin structure.
- Sir2p's role in inhibiting DNA replication at specific origins suggests a mechanism linked to unique origin features.
Purpose of the Study:
- To identify and characterize SIR2-sensitive DNA replication origins.
- To elucidate the structural elements and mechanisms by which Sir2p inhibits origin activity.
- To investigate the role of chromatin structure in Sir2p-mediated replication inhibition.
Main Methods:
- Identification of SIR2-sensitive origins on chromosomes III and VI.
- Linker scan analysis to map functional elements within origins.
- Assays to determine the requirement of SIR2 and specific DNA sequences for inhibition.
- Analysis of nucleosome positioning and the effect of nucleosome exclusion on origin activity.
Main Results:
- Five SIR2-sensitive origins were identified.
- A common organization was found, including an inhibitory sequence (I(S)) 3' to ORC binding sites.
- The I(S) element's inhibitory activity was dependent on SIR2.
- I(S) elements were located within positioned nucleosomes, and their exclusion relieved inhibition.
Conclusions:
- Sir2p inhibits DNA replication origins through a specific inhibitory sequence (I(S)).
- Sir2p and I(S) function by promoting a chromatin structure unfavorable for pre-RC assembly.
- Nucleosome positioning plays a critical role in Sir2p-mediated origin inhibition.
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