Involved in both the vernalization and photoperiod pathways by regulating expression of the related floral repressors FLOWERING LOCUS C (FLC) and FLOWERING LOCUS M (FLM). Together with VIN3, required during vernalization for the modifications of FLC and FLM chromatin that are associated with an epigenetically silenced state (e.g. chromatin modifications, histone deacetylation, and trimethylated H3 'Lys-4' H3K4me3 and 'Lys-27' H3K27me3) and with acquisition of competence to flower. Promotes flowering in short days (SD=8 hours light/16 hours dark). Associates dynamically at FLC locus; during vernalization, binds to specific sites, but when in warm conditions, distributed along the whole locus. Interacts with VIN3 and VIL2. The heterodimer made of VIN3 and VIL1 is required for establishing the vernalization-induced epigenetic silencing of FLC. Component of the plant homeodomain / polycomb repressive complex 2 (PHD-PRC2) large complex during prolonged cold, composed of core PRC2 components (VRN2, EZA1, FIE and MSI1), and three related PHD finger proteins (VIL1, VIL2 and VIN3) that mediates histone H3 trimethylation on 'Lys-27' (H3K27me3). Probably DNA-associated. Accumulates in shoot and root apices, and in leaves. Expressed at higher levels in short days (SD=8 hours light/16 hours dark) than in long days (LD=16 hours light/8 hours dark). Slightly induced by long cold exposure (e.g. 40 days at 4 degrees Celsius). Impaired vernalization response with incomplete repression of FLC during and after cold exposure, due to a reduction in vernalization-induced histone H3 deacetylation and methylation (e.g. H3K4me3 and H3K27me3). Delayed flowering in short days (SD=8 hours light/16 hours dark) conditions but not in long days (LD=16 hours light/8 hours dark); enhanced FLM levels dur to an enhance level of chromatin acetylation.