Transcription factor involved in the regulation of the circadian clock. Acts as a repressor of CCA1 by binding to its promoter. No binding to the LHY promoter. Interacts (via N-terminus) with APRR1/TOC1 (PubMed:19286557). Interacts with SPL (PubMed:25527103). Expressed in leaves, roots, and stems. No effect on the period length or phase of the circadian clock.