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Yeast G1 cyclins are unstable in G1 phase
B L Schneider1, E E Patton, S Lanker
1Cold Spring Harbor Laboratory, New York 11724, USA.
Nature
|September 17, 1998
Summary
G1 cyclins are unstable before the cell division Start, independent of mitotic cyclins. This instability links cyclin activity to transcription and protein synthesis rates in early cell cycle phases.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Cell division commitment in eukaryotes occurs at Start (yeast) or the restriction point (mammals).
- This critical transition is regulated by cyclin-dependent kinase Cdc28 and G1 cyclins (Cln1-3).
- While CLN gene transcription is cell-cycle regulated, G1 cyclin protein stability remains unclear.
Purpose of the Study:
- To investigate whether G1 cyclin protein stability is regulated during the cell cycle.
- To determine the role of mitotic cyclins in G1 cyclin turnover.
Main Methods:
- Analysis of G1 cyclin stability in Saccharomyces cerevisiae.
- Assessment of the requirement for Clb-Cdc28 activity in G1 cyclin turnover.
Main Results:
- G1 cyclins (Cln1-3) are inherently unstable during the G1 phase.
- G1 cyclin instability occurs independently of Clb-Cdc28 activity.
- This instability is not triggered by mitotic cyclins.
Conclusions:
- G1 cyclin instability is a key mechanism regulating cell cycle progression.
- This instability couples cyclin activity to transcriptional control and protein synthesis rates before Start.
- Provides a novel insight into the regulation of cell division commitment.