Circadian phase-specific degradation of the F-box protein ZTL is mediated by the proteasome.
Critical to the maintenance of circadian rhythmicity is the cyclic expression of at least some components of the central oscillator. High-amplitude cycling of mRNA and protein abundance, protein phosphorylation and nuclear/cytoplasmic shuttling have all been implicated in the maintenance of circadian period. Here we use a newly characterized Arabidopsis suspension cell culture to establish that the rhythmic changes in the levels of the clock-associated F-box protein, ZTL, are posttranscriptionally controlled through different circadian phase-specific degradation rates. This proteolysis is proteasome dependent, implicating ZTL itself as substrate for ubiquitination. This demonstration of circadian phase-regulated degradation of an F-box protein, which itself controls circadian period, suggests a novel regulatory feedback mechanism among known circadian systems.[1]References
- Circadian phase-specific degradation of the F-box protein ZTL is mediated by the proteasome. Kim, W.Y., Geng, R., Somers, D.E. Proc. Natl. Acad. Sci. U.S.A. (2003) [Pubmed]
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