Transcriptional regulation and function of the <i>Neurospora</i> clock gene <i>white collar 2</i> and its isoforms

Neiss, Andrea; Schafmeier, Tobias; Brunner, Michael

doi:10.1038/embor.2008.113

Cited by 19 publications

(26 citation statements)

References 24 publications

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“…Experiments with promoter deletions or fusions between lightresponsive promoters to reporter genes have identified DNA segments required for light regulation in several Neurospora genes, including al-3 (Carattoli et al, 1994), ccg-2 (Bell-Pedersen et al, 1996, frq (Froehlich et al, 2002), wc-1 (Káldi et al, 2006), and wc-2 (Neiss et al, 2008). Our results with con-10::lacZ translational fusions have simplified the number of segments that regulate con-10 activation by light.…”

Section: Regulation By Light Of Con-10 and Con-6 Transcriptionmentioning

confidence: 50%

A complex photoreceptor system mediates the regulation by light of the conidiation genes con-10 and con-6 in Neurospora crassa

Olmedo

Ruger-Herreros

Luque

et al. 2010

Fungal Genetics and Biology

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Section: Regulation By Light Of Con-10 and Con-6 Transcriptionmentioning

confidence: 50%

A complex photoreceptor system mediates the regulation by light of the conidiation genes con-10 and con-6 in Neurospora crassa

Olmedo

Ruger-Herreros

Luque

et al. 2010

Fungal Genetics and Biology

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“…Cytosol and nuclear extract were incubated with and without PPase inhibitors for 30 min at 37°C. WC-2 and its short isoform (sWC-2) (Neiss et al 2008) were analyzed by Western blotting. Arrowheads indicate hyperphosphorylated forms.…”

Section: Resultsmentioning

confidence: 99%

“…The negative feedback of FRQ on WCC activity is connected to a positive loop, in which FRQ supports accumulation of high levels of WCC (Lee et al 2000;Cheng et al 2001;Schafmeier et al 2006;Brunner and Kaldi 2008). Despite transcriptional regulation of wc-1 and wc-2 Brunner and Kaldi 2008;Neiss et al 2008), positive feedback strictly depends on post-translational regulation (Lee et al 2000;Cheng et al 2001;Schafmeier et al 2006). The molecular basis of positive feedback is not known.…”

mentioning

confidence: 99%

Circadian activity and abundance rhythms of the Neurospora clock transcription factor WCC associated with rapid nucleo–cytoplasmic shuttling

Schafmeier

Diernfellner²,

Schäfer³

et al. 2008

Genes Dev.

Self Cite

125

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The Neurospora clock protein FREQUENCY (FRQ) inhibits its transcriptional activator WHITE COLLAR COMPLEX (WCC) in a negative feedback loop and supports its accumulation in a positive loop. We show that positive feedback is a delayed effect of negative feedback underlying the same post-translational mechanisms: DNA-binding-competent active WCC commits rapidly to degradation. FRQ-dependent phosphorylation of WCC, which interferes with DNA binding (negative feedback), leads to reduced turnover and slow accumulation of newly expressed WCC (positive feedback). When DNA binding of WCC is compromised by mutation, its accumulation is independent of FRQ. Cycles of FRQ-dependent inactivation and PP2A-dependent reactivation of WCC occur in the minute range and are coupled to obligate rapid cycles of nucleo-cytoplasmic shuttling. WCC shuttling and activity cycles are modulated by FRQ in circadian fashion. We show here that FRQ supports negative and positive limbs of the clock by the same molecular mechanisms. Positive feedback (FRQ-dependent accumulation of WCC) is a delayed consequence of negative feedback (FRQ-dependent inactivation of WCC) rather than a mechanistically distinct feedback loop: WCC is active when FRQ is low or absent. Our data indicate that DNAbinding-competent, active WCC is unstable and rapidly turned over. FRQ-dependent phosphorylation of WCC interferes with DNA binding. This results in reduced turnover and allows accumulation of newly expressed WCC. Inactivation and reactivation of WCC are coupled to cycles of nucleo-cytoplasmic shuttling. We show that PP2A/RGB-1 activity is cytoplasmic, and hence passage of the WCC through the cytosol is obligatory for reactivation. Surprisingly, phosphorylation and shuttling cycles occur in the range of minutes and are modulated by FRQ in circadian fashion. Results and DiscussionWe investigated whether FRQ affects turnover of the WCC. In wild type, WCC is stable in constant darkness (DD) but turned over rapidly in constant light (LL) (Lee et al. 2000). To assess the influence of FRQ on WCC turnover, cultures of wild type and frq 9 , a mutant strain harboring a nonfunctional frq allele, were grown in LL. Turnover kinetics were then measured in the presence of cycloheximide (CHX). Degradation of WCC was substantially faster in frq 9 (t 1/2 ∼ 2.4 h) than in wild type (t 1/2 ∼ 4.2 h), demonstrating that FRQ stabilizes the light-activated WCC (Fig. 1A,F).In the negative feedback loop, FRQ promotes phosphorylation of WCC, which leads to its inactivation (Schafmeier et al. 2005). To investigate whether WCC activity affects its stability, we analyzed turnover of WCC in the wc-2G3 strain (Linden et al. 1997). wc-2G3 encodes a WC-2 version that lacks the C-terminal Zincfinger (Zn-finger) domain (Fig. 1B) and is henceforth referred to as wc2⌬C. WC-1 is unstable and does not accumulate in the absence of its assembly partner WC-2 (Cheng et al. 2002). WC-1 accumulated in high levels in wc-2⌬C (Fig. 1C), demonstrating that it assembled with the truncated WC-2⌬C. However, the mutan...

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“…One of these is an autoregulatory loop, in which the WCC supports its own expression at the transcriptional level (76,117). In the other loop, FRQ positively controls WCC levels by a mechanism that is most probably tightly coupled to the negative feedback.…”

Section: Fig 1 Principles Of the Race-tube Assay (A) Upper Panelmentioning

confidence: 99%

Interconnections of Reactive Oxygen Species Homeostasis and Circadian Rhythm inNeurospora crassa

Gyöngyösi

Káldi

2014

Antioxidants & Redox Signaling

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Significance: Both circadian rhythm and the production of reactive oxygen species (ROS) are fundamental features of aerobic eukaryotic cells. The circadian clock enhances the fitness of organisms by enabling them to anticipate cycling changes in the surroundings. ROS generation in the cell is often altered in response to environmental changes, but oscillations in ROS levels may also reflect endogenous metabolic fluctuations governed by the circadian clock. On the other hand, an effective regulation and timing of antioxidant mechanisms may be crucial in the defense of cellular integrity. Thus, an interaction between the circadian timekeeping machinery and ROS homeostasis or signaling in both directions may be of advantage at all phylogenetic levels. Recent Advances: The Frequency-White Collar-1 and White Collar-2 oscillator (FWO) of the filamentous fungus Neurospora crassa is well characterized at the molecular level. Several members of the ROS homeostasis were found to be controlled by the circadian clock, and ROS levels display circadian rhythm in Neurospora. On the other hand, multiple data indicate that ROS affect the molecular oscillator. Critical Issues: Increasing evidence suggests the interplay between ROS homeostasis and oscillators that may be partially or fully independent of the FWO. In addition, ROS may be part of a complex cellular network synchronizing non-transcriptional oscillators with timekeeping machineries based on the classical transcription-translation feedback mechanism. Future Directions: Further investigations are needed to clarify how the different layers of the bidirectional interactions between ROS homeostasis and circadian regulation are interconnected. Antioxid. Redox Signal. 20,[3007][3008][3009][3010][3011][3012][3013][3014][3015][3016][3017][3018][3019][3020][3021][3022][3023]

show abstract

Transcriptional regulation and function of the Neurospora clock gene white collar 2 and its isoforms

Cited by 19 publications

References 24 publications

A complex photoreceptor system mediates the regulation by light of the conidiation genes con-10 and con-6 in Neurospora crassa

A complex photoreceptor system mediates the regulation by light of the conidiation genes con-10 and con-6 in Neurospora crassa

Circadian activity and abundance rhythms of the Neurospora clock transcription factor WCC associated with rapid nucleo–cytoplasmic shuttling

Interconnections of Reactive Oxygen Species Homeostasis and Circadian Rhythm inNeurospora crassa

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