Transcriptional activator that exhibits a unique DNA binding specificity for CpG unmethylated motifs with a preference for CpGG. Component of the SET1 complex, at least composed of the catalytic subunit (SETD1A or SETD1B), WDR5, WDR82, RBBP5, ASH2L/ASH2, CXXC1/CFP1 HCFC1 and DPY30. Interacts with SETD1A. Interacts with ZNF335. Interacts with PRDM9; this interaction does not link PRDM9-activated recombination hotspot sites with DSB machinery and is not required for the hotspot recognition pathway. Interacts with histone H3K4me3 (By similarity). Associated with euchromatin. During mitosis, excluded from condensed chromosomes. Ubiquitous. The acidic domain carries the potential to activate transcription. May be regulated by proteolysis.