Histone-binding component that specifically recognizes H3 tails trimethylated on 'Lys-4' (H3K4me3), which mark transcription start sites of virtually all active genes (By similarity). Transcriptional regulator that binds specifically to DNA sequences 5'-GNGGTG-3' or 5'-GTGGNG-3', including promoter elements of the salt-inducible PRP2 gene. Plays a role in salinity tolerance. Interacts with H3K4me3 and to a lesser extent with H3K4me2. Predominantly expressed in the roots. By NaCl. The PHD-type zinc finger mediates the binding to H3K4me3. Belongs to the Alfin family.