Histone-lysine N-methyltransferase ATXR3, also known as protein SET DOMAIN GROUP 2 (SDG2), is a histone methyltransferase specifically required for trimethylation of Lys-4 of histone H3 (H3K4me3) and is crucial for both sporophyte and gametophyte development [1,2]. This is the POST_SET domain located at the C-terminal of SDG2, although there is no significant sequence homology with other Arabidopsis SDGs outside of the SET domain [2].

1: Arabidopsis SET DOMAIN GROUP2 is required for H3K4 trimethylation and is crucial for both sporophyte and gametophyte development. Berr A, McCallum EJ, Menard R, Meyer D, Fuchs J, Dong A, Shen WH; Plant Cell. 2010;22:3232-3248. PMID:21037105

2: SET DOMAIN GROUP2 is the major histone H3 lysine [corrected] 4 trimethyltransferase in Arabidopsis. Guo L, Yu Y, Law JA, Zhang X; Proc Natl Acad Sci U S A. 2010;107:18557-18562. PMID:20937886