Transcriptional activator of evening element (EE)-containing clock-controlled genes. Forms a negative feedback loop with APRR5. Regulates the pattern of histone H3 acetylation of the TOC1 promoter. Circadian-regulation. Peak of expression in the afternoon. Down-regulated by cold. Delay and reduction in levels of evening-phased clock gene transcripts and long circadian period. Subject to temperature associated alternative splicing producing mainly non-productive mRNAs.