Circadian clock component involved in the generation of biological rhythms, in particular in rhythm stability, period length, and temperature compensation. Oscillates in abundance with a daily peak early in the morning. Behaves as a negative element in circadian transcriptional loop. May bind to wc-2 protein. The complex frq-wc-2 may turn off the expression of frq. By light; perhaps through white collar-1 (wc-1) and white collar-2 (wc-2). Also activated directly by wc-1 and wc-2. Progressive phosphorylation during the late circadian day and early night. Phosphorylation is also involved in regulating frq degradation. Phosphorylation by CKII may have at least three functions; it decreases the stability of frq, reduces the protein complex formation between frq and the white collar proteins, and is important for the closing of the Neurospora circadian negative feedback loop. Maintains rhythms at high temperature (30 degrees Celsius). Maintains rhythms at lower temperature (18 degrees Celsius). Belongs to the FRQ family.