TY  - JOUR
A1  - Szabó, Áron
A1  - Papin, Christian
A1  - Zorn, Daniela
A1  - Ponien, Prishila
A1  - Weber, Frank
A1  - Raabe, Thomas
A1  - Rouyer, François
T1  - The CK2 Kinase Stabilizes CLOCK and Represses Its Activity in the Drosophila Circadian Oscillator
JF  - PLoS Biology
N2  - Phosphorylation is a pivotal regulatory mechanism for protein stability and activity in circadian clocks regardless of their evolutionary origin. It determines the speed and strength of molecular oscillations by acting on transcriptional activators and their repressors, which form negative feedback loops. In Drosophila, the CK2 kinase phosphorylates and destabilizes the PERIOD (PER) and TIMELESS (TIM) proteins, which inhibit CLOCK (CLK) transcriptional activity. Here we show that CK2 also targets the CLK activator directly. Downregulating the activity of the catalytic alpha subunit of CK2 induces CLK degradation, even in the absence of PER and TIM. Unexpectedly, the regulatory beta subunit of the CK2 holoenzyme is not required for the regulation of CLK stability. In addition, downregulation of \(CK2\alpha\) activity decreases CLK phosphorylation and increases per and tim transcription. These results indicate that CK2 inhibits CLK degradation while reducing its activity. Since the CK1 kinase promotes CLK degradation, we suggest that CLK stability and transcriptional activity result from counteracting effects of CK1 and CK2.
KW  - negative feedback loop
KW  - PER-TIM complex
KW  - posttranslational regulation
KW  - transcription factor
KW  - in-vivo
KW  - behavioral rhythms
KW  - proteins period
KW  - beta-subunit
KW  - phosphorylation
KW  - gene
KW  - CT, circadian time
KW  - LD, light:dark
KW  - DD, constant darkness
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127234
SN  - 1545-7885
VL  - 11
IS  - 8
ER  - 
TY  - JOUR
A1  - Vieira, Jacqueline
A1  - Jones, Alex R.
A1  - Danon, Antoine
A1  - Sakuma, Michiyo
A1  - Hoang, Nathalie
A1  - Robles, David
A1  - Tait, Shirley
A1  - Heyes, Derren J.
A1  - Picot, Marie
A1  - Yoshii, Taishi
A1  - Helfrich-Förster, Charlotte
A1  - Soubigou, Guillaume
A1  - Coppee, Jean-Yves
A1  - Klarsfeld, André
A1  - Rouyer, Francois
A1  - Scrutton, Nigel S.
A1  - Ahmad, Margaret
T1  - Human Cryptochrome-1 Confers Light Independent Biological Activity in Transgenic Drosophila Correlated with Flavin Radical Stability
JF  - PLoS One
N2  - Cryptochromes are conserved flavoprotein receptors found throughout the biological kingdom with diversified roles in plant development and entrainment of the circadian clock in animals. Light perception is proposed to occur through flavin radical formation that correlates with biological activity in vivo in both plants and Drosophila. By contrast, mammalian (Type II) cryptochromes regulate the circadian clock independently of light, raising the fundamental question of whether mammalian cryptochromes have evolved entirely distinct signaling mechanisms. Here we show by developmental and transcriptome analysis that Homo sapiens cryptochrome - 1 (HsCRY1) confers biological activity in transgenic expressing Drosophila in darkness, that can in some cases be further stimulated by light. In contrast to all other cryptochromes, purified recombinant HsCRY1 protein was stably isolated in the anionic radical flavin state, containing only a small proportion of oxidized flavin which could be reduced by illumination. We conclude that animal Type I and Type II cryptochromes may both have signaling mechanisms involving formation of a flavin radical signaling state, and that light independent activity of Type II cryptochromes is a consequence of dark accumulation of this redox form in vivo rather than of a fundamental difference in signaling mechanism.
KW  - arabidopsi
KW  - dependent magnetosensitvity
KW  - protein
KW  - clock
KW  - gene
KW  - mechanism
KW  - rhythm
KW  - oscillator
KW  - circadian photoreception
KW  - mammalian CRY1
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-134513
VL  - 7
IS  - 3
ER  -