Activity of the circadian transcription factor White Collar Complex is modulated by phosphorylation of SP-motifs

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 24 h. 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.Structured summaryMINT-7033869: WC-2 (uniprotkb:P78714) physically interacts (MI:0218) with WC-1 (uniprotkb:Q01371) by tandem-affinity purification (MI:0676)MINT-7033885: WC-2 (uniprotkb:P78714) physically interacts (MI:0218) with FRQ (uniprotkb:P19970) and WC-1 (uniprotkb:Q01371) by cross-linking studies (MI:0030)