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Cyclin A degradation employs preferentially used lysines and a cyclin box function other than Cdk1 binding

Vimal Ramachandran1, Matthias Matzkies, Axel Dienemann

  • 1Institute for Genetics, University of Cologne, Cologne, Germany.

Cell Cycle (Georgetown, Tex.)
|February 23, 2007
PubMed

Insights

Drosophila Cyclin A destruction requires synergistic N- and C-terminal signals for recognition by the anaphase promoting complex/cyclosome (APC/C). Specific lysine residues are crucial for ubiquitination and subsequent degradation during mitosis.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Cyclin A is degraded during mitosis by the anaphase promoting complex/cyclosome (APC/C).
  • Mitotic destruction of Cyclin A persists even when the spindle assembly checkpoint inhibits other APC/C substrates.
  • A complex N-terminal destruction signal, rather than a simple destruction box, has been previously implicated in Cyclin A degradation.

Purpose of the Study:

  • To investigate the specific N- and C-terminal regions and residues involved in Drosophila Cyclin A destruction.
  • To elucidate the synergistic action of different protein domains in APC/C-mediated degradation.
  • To identify key lysine residues essential for Cyclin A ubiquitination and proteolysis.

Main Methods:

  • Site-directed mutagenesis of specific N-terminal (KEN box, D-box, Asp70) and C-terminal (cyclin box) elements.
  • Analysis of Cyclin A destruction kinetics in response to mutations during mitosis.
  • Mutation of potential ubiquitin acceptor lysines near N-terminal signals.

Main Results:

  • Both N- and C-terminal residues contribute synergistically to Drosophila Cyclin A recognition and degradation by the APC/C.
  • The first KEN box, first D-box, Asp70, and the cyclin box are essential for mitotic destruction.
  • Specific N-terminal lysines are preferentially used for ubiquitination, and their mutation leads to mitotic stability.
  • The cyclin box may mediate spindle checkpoint-independent APC/C recognition, independent of Cdk1 binding.

Conclusions:

  • Drosophila Cyclin A degradation is a complex process requiring coordinated signals from both protein termini.
  • Specific lysines act as critical ubiquitin acceptor sites, facilitating APC/C-mediated proteolysis.
  • The cyclin box plays a dual role in Cyclin A function, influencing both APC/C recognition and potentially cell cycle progression.

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