What makes ribosomes tick?

Mills, Sarah Catherine; Enganti, Ramya; Arnim, Albrecht G. von

doi:10.1080/15476286.2017.1391444

Cited by 12 publications

(5 citation statements)

References 88 publications

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“…This does not exclude that oscillating mRNAs also contribute to the regulation of non‐fluctuating proteins if the degradation and synthesis rates of these proteins are changing during the diurnal cycle. In Arabidopsis, there is increasing evidence of diurnal and photoperiodic dynamics of mRNA translation (Mills, Enganti, & von Arnim, 2018; Seaton et al, 2018). If dynamic regulation of protein degradation and synthesis is coupled to differential ribosomal loading of oscillating mRNAs, this would result in stable diurnal protein levels.…”

Section: Resultsmentioning

confidence: 99%

Diurnal dynamics of the Arabidopsis rosette proteome and phosphoproteome

Uhrig

Echevarría-Zomeño

Schläpfer

et al. 2020

Plant Cell & Environment

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Plant growth depends on the diurnal regulation of cellular processes, but it is not well understood if and how transcriptional regulation controls diurnal fluctuations at the protein level. Here, we report a high‐resolution Arabidopsis thaliana (Arabidopsis) leaf rosette proteome acquired over a 12 hr light:12 hr dark diurnal cycle and the phosphoproteome immediately before and after the light‐to‐dark and dark‐to‐light transitions. We quantified nearly 5,000 proteins and 800 phosphoproteins, of which 288 fluctuated in their abundance and 226 fluctuated in their phosphorylation status. Of the phosphoproteins, 60% were quantified for changes in protein abundance. This revealed six proteins involved in nitrogen and hormone metabolism that had concurrent changes in both protein abundance and phosphorylation status. The diurnal proteome and phosphoproteome changes involve proteins in key cellular processes, including protein translation, light perception, photosynthesis, metabolism and transport. The phosphoproteome at the light–dark transitions revealed the dynamics at phosphorylation sites in either anticipation of or response to a change in light regime. Phosphorylation site motif analyses implicate casein kinase II and calcium/calmodulin‐dependent kinases among the primary light–dark transition kinases. The comparative analysis of the diurnal proteome and diurnal and circadian transcriptome established how mRNA and protein accumulation intersect in leaves during the diurnal cycle of the plant.

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Section: Resultsmentioning

confidence: 99%

Diurnal dynamics of the Arabidopsis rosette proteome and phosphoproteome

Uhrig

Echevarría-Zomeño

Schläpfer

et al. 2020

Plant Cell & Environment

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“…In the brain of Drosophila , expression of the Tor gene shows a bimodal pattern in light/dark cycles, and rhythmic changes in neuron morphology depend on expression of Tor [ 52 ]. An important output of the clock is gene expression; the role of the circadian clock in regulating gene transcription is well known, and recent findings have shown that the clock is also able to regulate specific genes at the level of translation in several organisms [ 53 , 54 ] including Neurospora [ 55 ]. The TOR pathway can play a role in this translational regulation: in mouse cells, mTORC1 activity is rhythmic [ 56 ], which drives rhythmic phosphorylation of 4E-BP1 and rhythmic translation of proteins [ 57 ].…”

Section: Discussionmentioning

confidence: 99%

A component of the TOR (Target Of Rapamycin) nutrient-sensing pathway plays a role in circadian rhythmicity in Neurospora crassa

et al. 2018

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The TOR (Target of Rapamycin) pathway is a highly-conserved signaling pathway in eukaryotes that regulates cellular growth and stress responses. The cellular response to amino acids or carbon sources such as glucose requires anchoring of the TOR kinase complex to the lysosomal/vacuolar membrane by the Ragulator (mammals) or EGO (yeast) protein complex. Here we report a connection between the TOR pathway and circadian (daily) rhythmicity. The molecular mechanism of circadian rhythmicity in all eukaryotes has long been thought to be transcription/translation feedback loops (TTFLs). In the model eukaryote Neurospora crassa, a TTFL including FRQ (frequency) and WCC (white collar complex) has been intensively studied. However, it is also well-known that rhythmicity can be seen in the absence of TTFL functioning. We previously isolated uv90 as a mutation that compromises FRQ-less rhythms and also damps the circadian oscillator when FRQ is present. We have now mapped the uv90 gene and identified it as NCU05950, homologous to the TOR pathway proteins EGO1 (yeast) and LAMTOR1 (mammals), and we have named the N. crassa protein VTA (vacuolar TOR-associated protein). The protein is anchored to the outer vacuolar membrane and deletion of putative acylation sites destroys this localization as well as the protein’s function in rhythmicity. A deletion of VTA is compromised in its growth responses to amino acids and glucose. We conclude that a key protein in the complex that anchors TOR to the vacuole plays a role in maintaining circadian (daily) rhythmicity. Our results establish a connection between the TOR pathway and circadian rhythms and point towards a network integrating metabolism and the circadian system.

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“…Ribosome loading of mRNAs is also under the control of the circadian clock, as indicated by broad changes in the phase and amplitude of diel translation in a clock-deficient strain. The mRNAs for ribosomal proteins are among those with the most pronounced and coordinated changes in diel ribosome loading ( Missra et al, 2015 ; Mills et al, 2017 ). These findings indicate that signals from the light environment and signals from the circadian clock must be integrated as they converge onto the translation apparatus.…”

Section: Introductionmentioning

confidence: 99%

Phosphorylation of Ribosomal Protein RPS6 Integrates Light Signals and Circadian Clock Signals

et al. 2018

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The translation of mRNA into protein is tightly regulated by the light environment as well as by the circadian clock. Although changes in translational efficiency have been well documented at the level of mRNA-ribosome loading, the underlying mechanisms are unclear. The reversible phosphorylation of RIBOSOMAL PROTEIN OF THE SMALL SUBUNIT 6 (RPS6) has been known for 40 years, but the biochemical significance of this event remains unclear to this day. Here, we confirm using a clock-deficient strain of Arabidopsis thaliana that RPS6 phosphorylation (RPS6-P) is controlled by the diel light-dark cycle with a peak during the day. Strikingly, when wild-type, clock-enabled, seedlings that have been entrained to a light-dark cycle are placed under free-running conditions, the circadian clock drives a cycle of RPS6-P with an opposite phase, peaking during the subjective night. We show that in wild-type seedlings under a light-dark cycle, the incoherent light and clock signals are integrated by the plant to cause an oscillation in RPS6-P with a reduced amplitude with a peak during the day. Sucrose can stimulate RPS6-P, as seen when sucrose in the medium masks the light response of etiolated seedlings. However, the diel cycles of RPS6-P are observed in the presence of 1% sucrose and in its absence. Sucrose at a high concentration of 3% appears to interfere with the robust integration of light and clock signals at the level of RPS6-P. Finally, we addressed whether RPS6-P occurs uniformly in polysomes, non-polysomal ribosomes and their subunits, and non-ribosomal protein. It is the polysomal RPS6 whose phosphorylation is most highly stimulated by light and repressed by darkness. These data exemplify a striking case of contrasting biochemical regulation between clock signals and light signals. Although the physiological significance of RPS6-P remains unknown, our data provide a mechanistic basis for the future understanding of this enigmatic event.

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What makes ribosomes tick?

Cited by 12 publications

References 88 publications

Diurnal dynamics of the Arabidopsis rosette proteome and phosphoproteome

Diurnal dynamics of the Arabidopsis rosette proteome and phosphoproteome

A component of the TOR (Target Of Rapamycin) nutrient-sensing pathway plays a role in circadian rhythmicity in Neurospora crassa

Phosphorylation of Ribosomal Protein RPS6 Integrates Light Signals and Circadian Clock Signals

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