Related Experiment Video
Updated: Oct 3, 2026
Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations
Published on: September 17, 2012
The KEN box regulates Clb2 proteolysis in G1 and at the metaphase-to-anaphase transition
C Hendrickson1, M A Meyn, L Morabito
1Department of Genetics, Howard Hughes Medical Institute, University of Pennsylvania Medical School, 446 CRB, 415 Curie Boulevard, Philadelphia, PA 19104, USA.
Abstract:
Clb2 mitotic cyclin inhibits cell cycle progression by preventing mitotic exit and DNA synthesis. To allow cell cycle progression, Clb2 proteolysis is triggered by Cdc20 during the metaphase-to-anaphase (M-A) transition and by Hct1 during mitotic exit and G1 [1-6]. A cis element called the destruction box is required for this proteolysis [7-11]. Recently, an additional cis element called the "KEN box" was also shown to be required for proteolysis of human CDC20 and Securin [3,12]. Using a novel color assay, we show that a Clb2 KEN box is required to target a fusion protein containing the first 124 amino acids of Clb2 for proteolysis. We further show that full-length Clb2 bearing mutations in the KEN box is degraded efficiently during the M-A transition, but poorly during G1. If the destruction box of Clb2 is mutated in combination with mutation of the KEN box, then this form of Clb2 is more stable than Clb2 bearing either mutation by itself during both M-A and G1. Our results show that the KEN box and the destruction box act together during both M-A and G1 to regulate Clb2 proteolysis.
Insights
The KEN box and destruction box cooperate to regulate Clb2 proteolysis, a key mitotic cyclin. Mutations in both boxes stabilize Clb2, impacting cell cycle progression.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Clb2 mitotic cyclin controls cell cycle progression by inhibiting mitotic exit and DNA synthesis.
- Proteolysis of Clb2 is essential for cell cycle progression, regulated by Cdc20 and Hct1 during specific cell cycle phases.
- Both the destruction box and the KEN box are cis elements critical for Clb2 proteolysis.
Purpose of the Study:
- To investigate the role of the Clb2 KEN box in targeting Clb2 for proteolysis.
- To determine how the KEN box and destruction box cooperate in regulating Clb2 stability throughout the cell cycle.
Main Methods:
- Utilized a novel color assay to assess Clb2 proteolysis.
- Generated mutations in the KEN box and destruction box of Clb2.
- Analyzed the stability of mutated Clb2 during the metaphase-to-anaphase transition and G1 phase.
Main Results:
- A Clb2 KEN box is required for the proteolysis of a Clb2 fusion protein.
- Full-length Clb2 with a mutated KEN box shows impaired degradation during G1.
- Combined mutations in both the KEN box and destruction box result in increased Clb2 stability during both metaphase-to-anaphase and G1 phases.
Conclusions:
- The KEN box and destruction box function synergistically to regulate Clb2 proteolysis.
- Both cis elements are crucial for controlling Clb2 stability during both the metaphase-to-anaphase transition and G1 phase of the cell cycle.
Related Concept Videos
02:15M-Cdk Drives Transition Into Mitosis
Cyclin-dependent kinases, or Cdks, work in concert with cyclins to control cell cycle transitions. M-Cdk, a complex of Cdk1 bound to M cyclin, is a well-known example of this coordinated control that drives the transition from the G2 to the M phase.
M cyclin...
02:15M-Cdk Drives Transition Into Mitosis
Cyclin-dependent kinases, or Cdks, work in concert with cyclins to control cell cycle transitions. M-Cdk, a complex of Cdk1 bound to M cyclin, is a well-known example of this coordinated control that drives the transition from the G2 to the M phase.
M cyclin...
02:17Separation of Sister Chromatids
At the onset of anaphase, separase, a proteolytic enzyme, is...
02:34Inhibition of Cdk Activity
01:28The Cell Cycle Control System
Cyclins and cyclin-dependent kinases (Cdks) are the primary cell cycle regulators and function at the cell...
02:11The Cell Cycle Control System