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Precocious S-phase entry in budding yeast prolongs replicative state and increases dependence upon Rad53 for
Julia M Sidorova1, Linda L Breeden
1Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA. jsidorov@fred.fhcrc.org
Genetics
|January 24, 2002
Summary
Overproducing the G1 regulator Swi4 in yeast causes precocious S phase entry and genomic instability, particularly in checkpoint-deficient cells. Rad53 activation is key to this process.
Area of Science:
- Cell Cycle Regulation
- Genomic Stability
- Molecular Biology
Background:
- Precocious entry into S phase, driven by G1 regulators, can lead to genomic instability.
- The precise mechanisms underlying this phenomenon remain largely unexplored.
Purpose of the Study:
- To investigate the consequences of precocious S phase entry induced by overproducing a deregulated form of the G1-specific transcriptional activator Swi4 (Swi4-t) in yeast.
- To elucidate the role of the Rad53 checkpoint kinase in response to Swi4-t-induced S phase alterations.
Main Methods:
- Overproduction of a deregulated Swi4 (Swi4-t) in wild-type and checkpoint-deficient (rad53-11) yeast strains.
- Monitoring cell viability, Rad53 kinase activity, and the G1 to S phase transition.
- Analysis of S phase duration, replication intermediates, and origin firing.
Main Results:
- Wild-type cells tolerated Swi4-t, but checkpoint-deficient rad53-11 cells exhibited reduced viability.
- Overproduction of Swi4-t led to increased Rad53 kinase activity, indicating checkpoint activation.
- Cells with Swi4-t showed precocious S phase entry, extended S phase duration, increased replication intermediates, and potentially more extensive origin firing.
Conclusions:
- Rad53 kinase activity is crucial for maintaining viability and genomic stability when S phase progression is accelerated by Swi4-t.
- Rad53 may modulate origin firing to optimize S phase rate and fidelity under conditions of perturbed cell cycle control.