Post-translational regulation of the Arabidopsis circadian clock through selective proteolysis and phosphorylation of pseudo- response regulator proteins Export

@article{citeulike:3088508, abstract = {The circadian clock controls the period, phasing and amplitude of processes which oscillate with a near 24 hour rhythm. One core group of clock components in Arabidopsis that controls the pace of the central oscillator is comprised of five PRR (PSEUDO-RESPONSE REGULATOR) proteins whose biochemical function in the clock remains unclear. Peak expression of TOC1 (TIMING OF CAB EXPRESSION 1)/PRR1, PRR3, PRR5, PRR7 and PRR9 are each phased differently over the course of the day and loss of any PRR protein alters period. Here we show that, together with TOC1, PRR5 is the only other likely proteolytic substrate of the E3 ubiquitin ligase SCF{not}ZTL within this PRR family. We further demonstrate a functional significance for the phosphorylated forms of PRR5, TOC1 and PRR3. Each PRR protein examined is nuclear-localized and is differentially phosphorylated over the circadian cycle. The more highly phosphorylated forms of PRR5 and TOC1 interact best with the F-box protein ZTL (ZEITLUPE), suggesting a mechanism to modulate their proteolysis. In vivo degradation of both PRR5 and ZTL is inhibited by blue light (BL), likely the result of BL photoperception by ZTL. TOC1 and PRR3 interact in vivo and phosphorylation of both is necessary for their optimal binding in vitro. Additionally, since PRR3 and ZTL both interact with TOC1 in vivo via the TOC1 N-terminus, taken together these data suggest that the TOC1/PRR3 phosphorylation-dependent interaction may protect TOC1 from ZTL-mediated degradation, resulting in an enhanced amplitude of TOC1 cycling. 10.1074/jbc.M803471200}, author = {Fujiwara, Sumire and Wang, Lei and Han, Linqu and Suh, Sung-Suk and Salome, Patrice A. and Mcclung, Robertson C. and Somers, David E.}, citeulike-article-id = {3088508}, citeulike-linkout-0 = {http://dx.doi.org/10.1074/jbc.M803471200}, citeulike-linkout-1 = {http://www.jbc.org/cgi/content/abstract/283/34/23073}, citeulike-linkout-2 = {http://view.ncbi.nlm.nih.gov/pubmed/18562312}, citeulike-linkout-3 = {http://www.hubmed.org/display.cgi?uids=18562312}, day = {18}, doi = {10.1074/jbc.M803471200}, journal = {J. Biol. Chem.}, keywords = {arabidopsis, circadian\_clock}, month = {June}, pages = {M803471200+}, posted-at = {2008-10-14 14:03:38}, priority = {4}, title = {Post-translational regulation of the Arabidopsis circadian clock through selective proteolysis and phosphorylation of pseudo- response regulator proteins}, url = {http://dx.doi.org/10.1074/jbc.M803471200}, year = {2008} }

TY - JOUR ID - citeulike:3088508 L3 - citeulike-article-id:3088508 N2 - The circadian clock controls the period, phasing and amplitude of processes which oscillate with a near 24 hour rhythm. One core group of clock components in Arabidopsis that controls the pace of the central oscillator is comprised of five PRR (PSEUDO-RESPONSE REGULATOR) proteins whose biochemical function in the clock remains unclear. Peak expression of TOC1 (TIMING OF CAB EXPRESSION 1)/PRR1, PRR3, PRR5, PRR7 and PRR9 are each phased differently over the course of the day and loss of any PRR protein alters period. Here we show that, together with TOC1, PRR5 is the only other likely proteolytic substrate of the E3 ubiquitin ligase SCF{not}ZTL within this PRR family. We further demonstrate a functional significance for the phosphorylated forms of PRR5, TOC1 and PRR3. Each PRR protein examined is nuclear-localized and is differentially phosphorylated over the circadian cycle. The more highly phosphorylated forms of PRR5 and TOC1 interact best with the F-box protein ZTL (ZEITLUPE), suggesting a mechanism to modulate their proteolysis. In vivo degradation of both PRR5 and ZTL is inhibited by blue light (BL), likely the result of BL photoperception by ZTL. TOC1 and PRR3 interact in vivo and phosphorylation of both is necessary for their optimal binding in vitro. Additionally, since PRR3 and ZTL both interact with TOC1 in vivo via the TOC1 N-terminus, taken together these data suggest that the TOC1/PRR3 phosphorylation-dependent interaction may protect TOC1 from ZTL-mediated degradation, resulting in an enhanced amplitude of TOC1 cycling. 10.1074/jbc.M803471200 JF - J. Biol. Chem. TI - Post-translational regulation of the Arabidopsis circadian clock through selective proteolysis and phosphorylation of pseudo- response regulator proteins SP - M803471200 KW - arabidopsis KW - circadian_clock AU - Fujiwara, Sumire AU - Wang, Lei AU - Han, Linqu AU - Suh, Sung-Suk AU - Salome, Patrice AU - Mcclung, Robertson AU - Somers, David PY - 2008/06/18/ UR - http://dx.doi.org/10.1074/jbc.M803471200 ER -