Probable histone demethylase that specifically demethylates 'Lys-4' of histone H3, a specific tag for epigenetic transcriptional activation, thereby acting as a corepressor. Acts by oxidizing the substrate by FAD to generate the corresponding imine that is subsequently hydrolyzed. Demethylates both mono- and di-methylated 'Lys-4' of histone H3 (By similarity). Participates in the transcriptional repression of the presenilin protein hop-1 (PubMed:12411496). May act via the formation of a multiprotein complex that remodel or modify the chromatin (PubMed:12381669). Together with met-2, set-17 and set-26, required for transgenerational fertility (PubMed:24685137). Probably part of a large repressor complex (PubMed:12411496). Interacts with CoREST protein spr-1 (PubMed:12411496). Interacts with chromobox protein homolog hpl-1 (PubMed:26476455). Expressed throughout the development. Expressed in embryos, L1, L2, L3 and L4 larval stages and in adults. Progressive loss of fertility and accumulation of histone H3 'Lys-4' dimethylation (H3K4me2) over generations (PubMed:24685137). Suppression of sel-12 mutant phenotypes, possibly by up-regulating hop-1 expression (PubMed:12411496). Belongs to the flavin monoamine oxidase family.