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Proteasome function is required for biological timing throughout the twenty-four hour cycle.

van Ooijen G, Dixon LE, Troein C, Millar AJ - Curr. Biol. (2011)

Bottom Line: TOC1 degradation peaks in response to darkness.Targeted protein degradation, unlike transcription and translation, is shown to be essential to sustain TTFL rhythmicity throughout the circadian cycle.Although proteasomal degradation is not necessary for sustained posttranslational oscillations in transcriptionally inactive cells, TTFL and posttranslational oscillators are normally coupled, and proteasome function is crucial to sustain both.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences and Centre for Systems Biology at Edinburgh, University of Edinburgh, The King's Buildings, Mayfield Road, Edinburgh EH9 3JD, UK. gerben.vanooijen@ed.ac.uk

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Effects of Proteasomal Inhibition(A) Period difference relative to vehicle-treated cells, resulting from treatment with indicated concentrations of epoxomicin or PYR-41 on CCA1-LUC (red bars) or pCCA1::LUC (black bars). Error bars represent standard deviation (SD; n = 8).(B) Effect of epoxomicin (blue traces, n = 4) or MG132 (red traces, n = 8) on CCA1-LUC in downward (top) or upward (bottom) phase, compared to vehicle (black traces, n = 8). See also Figure S2.
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fig2: Effects of Proteasomal Inhibition(A) Period difference relative to vehicle-treated cells, resulting from treatment with indicated concentrations of epoxomicin or PYR-41 on CCA1-LUC (red bars) or pCCA1::LUC (black bars). Error bars represent standard deviation (SD; n = 8).(B) Effect of epoxomicin (blue traces, n = 4) or MG132 (red traces, n = 8) on CCA1-LUC in downward (top) or upward (bottom) phase, compared to vehicle (black traces, n = 8). See also Figure S2.

Mentions: The widely used proteasome inhibitor MG132 increases the free-running period in a dose-dependent fashion in Ostreococcus [12]. MG132 is a trileucine aldehyde, inhibiting proteasome subunits β1 and β5, but it also targets papain-like cysteine proteases in plants [27]. To verify that modulating the proteasome pathway indeed affects the Ostreococcus free-running period, we analyzed the effects of the highly selective proteasome inhibitor epoxomicin [28], which inhibits all three catalytic proteasome subunits in plants [27]. Low micromolar concentrations of this drug resulted in robust period increases of ∼9–10 hr (Figure 2A and Figure S2A). Furthermore, an inhibitor (PYR-41) [29] that acts on the ubiquitin/proteasome pathway via inhibition of ubiquitin-activating enzymes yielded similar, albeit less potent, effects in the lengthening period (Figure 2A and Figure S2B). In combination, the effects of these inhibitors show that targeted protein degradation via the proteasome is indeed necessary to maintain rhythmicity.


Proteasome function is required for biological timing throughout the twenty-four hour cycle.

van Ooijen G, Dixon LE, Troein C, Millar AJ - Curr. Biol. (2011)

Effects of Proteasomal Inhibition(A) Period difference relative to vehicle-treated cells, resulting from treatment with indicated concentrations of epoxomicin or PYR-41 on CCA1-LUC (red bars) or pCCA1::LUC (black bars). Error bars represent standard deviation (SD; n = 8).(B) Effect of epoxomicin (blue traces, n = 4) or MG132 (red traces, n = 8) on CCA1-LUC in downward (top) or upward (bottom) phase, compared to vehicle (black traces, n = 8). See also Figure S2.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3102177&req=5

fig2: Effects of Proteasomal Inhibition(A) Period difference relative to vehicle-treated cells, resulting from treatment with indicated concentrations of epoxomicin or PYR-41 on CCA1-LUC (red bars) or pCCA1::LUC (black bars). Error bars represent standard deviation (SD; n = 8).(B) Effect of epoxomicin (blue traces, n = 4) or MG132 (red traces, n = 8) on CCA1-LUC in downward (top) or upward (bottom) phase, compared to vehicle (black traces, n = 8). See also Figure S2.
Mentions: The widely used proteasome inhibitor MG132 increases the free-running period in a dose-dependent fashion in Ostreococcus [12]. MG132 is a trileucine aldehyde, inhibiting proteasome subunits β1 and β5, but it also targets papain-like cysteine proteases in plants [27]. To verify that modulating the proteasome pathway indeed affects the Ostreococcus free-running period, we analyzed the effects of the highly selective proteasome inhibitor epoxomicin [28], which inhibits all three catalytic proteasome subunits in plants [27]. Low micromolar concentrations of this drug resulted in robust period increases of ∼9–10 hr (Figure 2A and Figure S2A). Furthermore, an inhibitor (PYR-41) [29] that acts on the ubiquitin/proteasome pathway via inhibition of ubiquitin-activating enzymes yielded similar, albeit less potent, effects in the lengthening period (Figure 2A and Figure S2B). In combination, the effects of these inhibitors show that targeted protein degradation via the proteasome is indeed necessary to maintain rhythmicity.

Bottom Line: TOC1 degradation peaks in response to darkness.Targeted protein degradation, unlike transcription and translation, is shown to be essential to sustain TTFL rhythmicity throughout the circadian cycle.Although proteasomal degradation is not necessary for sustained posttranslational oscillations in transcriptionally inactive cells, TTFL and posttranslational oscillators are normally coupled, and proteasome function is crucial to sustain both.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences and Centre for Systems Biology at Edinburgh, University of Edinburgh, The King's Buildings, Mayfield Road, Edinburgh EH9 3JD, UK. gerben.vanooijen@ed.ac.uk

Show MeSH
Related in: MedlinePlus