Fop, or Friend of Prmt1, proteins are conserved from fungi and plants to vertebrates. There is little that is actually conserved except for this C-terminal LDXXLDAYM region where X is any amino acid). The Fop proteins themselves are nuclear proteins localised to regions with low levels of DAPI, with a punctate/speckle-like distribution. Fop is a chromatin-associated protein and it co-localises with facultative heterochromatin. It is is critical for oestrogen-dependent gene activation [1].

1: Friend of Prmt1, a novel chromatin target of protein arginine methyltransferases. van Dijk TB, Gillemans N, Stein C, Fanis P, Demmers J, van de Corput M, Essers J, Grosveld F, Bauer UM, Philipsen S; Mol Cell Biol. 2010;30:260-272. PMID:19858291