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The cyclin C/Cdk8 kinase
Abstract:
Cyclin C was originally identified in a genetic screen for metazoan cDNAs that complement a triple knock-out of the CLN genes, involved in G1/S progression in S. cerevisiae. Unlike cyclin Ds and cyclin E, also identified in this screen, cyclin C has not been found to have a cell-cycle role in metazoa. Identified as the catalytic partner of cyclin C, Cdk8 is a novel protein-kinase of the Cdk family structurally related to the yeast Srb10 kinase. Cyclin C, Cdk8 and RNA polymerase II are found in a large multi-protein complex that shows structural as well as functional homologies with the yeast polymerase II holoenzyme. These observations and the sequence similarity to the kinase/cyclin pair Srb10/Srb11 in S. cerevisiae, suggest that cyclin C and Cdk8 control RNA polymerase II function.
Insights
Cyclin C and its partner Cdk8 were identified in a screen for cell cycle genes. This protein complex may regulate RNA polymerase II function in metazoans.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Cyclin C was identified through genetic screening for its ability to complement yeast cell cycle mutations.
- Unlike other cyclins (D, E), cyclin C's metazoan cell cycle role remained unclear.
- Cdk8, the catalytic partner of cyclin C, is a novel protein kinase.
Purpose of the Study:
- To investigate the function of cyclin C and its associated kinase, Cdk8.
- To explore the potential role of the cyclin C-Cdk8 complex in metazoan gene regulation.
Main Methods:
- Genetic screening in S. cerevisiae.
- Protein complex isolation and characterization.
- Sequence homology analysis.
Main Results:
- Cyclin C and Cdk8 form a large multi-protein complex with RNA polymerase II.
- This complex shares structural and functional similarities with the yeast RNA polymerase II holoenzyme.
- Sequence similarities suggest a conserved regulatory role.
Conclusions:
- The cyclin C-Cdk8 complex is implicated in controlling RNA polymerase II function.
- This finding suggests a conserved mechanism for regulating transcription across species.
- Further research is warranted to elucidate the precise regulatory role.