Transcriptional coactivator necessary for expression of the clock genes PRR5 and TOC1 (PubMed:25012192, PubMed:25848708). Antagonizes REV8 function in the regulation of anthocyanin accumulation (PubMed:25848001). Involved in red light input to the clock (PubMed:25012192). Activates clock-controlled genes with afternoon peak (PubMed:23818596). Mediates light inhibition of hypocotyl elongation (PubMed:23818596). Interacts with CCA1, LHY, REV4 and REV8, but not with PRR7 or PRR9. Expressed in roots, stems, leaves, seedlings, cotyledons, inflorescences and siliques. Highest expression in root tips, young leaves and vasculatur tissues. Circadian-regulation (PubMed:23818596, PubMed:25012192). Maximum levels of expression in the subjective morning (PubMed:23818596, PubMed:25012192). Up-regulated by a light pulse in the middle of the night via the phytochrome family of red/far-red light photoreceptors (PubMed:23818596, PubMed:25332490, PubMed:25012192). Up-regulated following a temperature upshift during the dark period (PubMed:24690904). Repressed by members of the TOC1/PRR1 family of clock genes (PubMed:23818596). No differences in hypocotyl length when grown in complete darkness, but longer hypocotyls in plants under continuous white or red light (PubMed:23818596). Lengthened circadian cycle (PubMed:25012192). Unable to bind to DNA, but recruited to the evening element (EE)-containing region of the PRR5 and TOC1 promoters through its interaction with the DNA binding proteins REV8 and REV4 (PubMed:25012192, PubMed:25848708). The evening complex (EC) nighttime repressor is implicated in the temperature responsiveness by binding to the LNK1 promoter (PubMed:25332490, PubMed:24690904). Responds also to some extent to a dark/light transition in an EC-independent manner (PubMed:25332490).