Histone methyltransferase that methylates 'Lys-4' of histone H3 (PubMed:17707229). H3 'Lys-4' methylation represents a specific tag for epigenetic transcriptional activation (PubMed:17707229). Plays a central role in beta-globin locus transcription regulation by being recruited by NFE2 (PubMed:17707229). Plays an important role in controlling bulk H3K4me during oocyte growth and preimplantation development (By similarity). Required during the transcriptionally active period of oocyte growth for the establishment and/or maintenance of bulk H3K4 trimethylation (H3K4me3), global transcriptional silencing that preceeds resumption of meiosis, oocyte survival and normal zygotic genome activation (By similarity).