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Updated: Jun 23, 2026

Rapid Analysis of Circadian Phenotypes in Arabidopsis Protoplasts Transfected with a Luminescent Clock Reporter
Published on: September 17, 2016
Activity of the circadian transcription factor White Collar Complex is modulated by phosphorylation of SP-motifs
Gencer Sancar1, Cigdem Sancar, Michael Brunner
1University of Heidelberg Biochemistry Center, Heidelberg, Germany.
Abstract:
Posttranslational modifications, particularly phosphorylation, regulate activity, stability and localization of proteins in circadian clocks, thereby contributing to a stable oscillation with a period of approximately 24h. The White Collar Complex (WCC) is the central transcription factor of the circadian clock of Neurospora crassa. Its activity is regulated in a circadian manner by rhythmic phosphorylation, mediated by the clock protein Frequency (FRQ). Here we present purification of TAP-tagged WCC and identification of novel phosphorylation sites of WC-1 and WC-2, all of which appear to be proline directed. Exchange of a single WC-2 serine residue (S433) to alanine or aspartate affects WCC-dependent transcription and circadian period, suggesting an important role of WC-2 S433 phosphorylation for WCC activity and circadian timing.
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