The extended plant homeodomain (ePHD) zinc finger is characterized as Cys2HisCys5HisCys2His. This entry represents the ePHD finger of Histone-lysine N-methyltransferase 2B (KMT2B), also known as MLL2. KMT2B is a second human homologue of Drosophila trithorax, located on chromosome 19 [, ]. It belongs to the MLL subfamily of H3K4-specific histone lysine methyltransferases (KMT2) and is vital for normal mammalian embryonic development []. KMT2B functions as the catalytic subunit in the MLL2 complex, which contains WDR5, RbBP5, ASH2L and DPY30 as integral core subunits required for the efficient methylation activity of the complex. The MLL2 complex is highly active and specific for histone 3 lysine 4 (H3K4) methylation, which stimulates chromatin transcription in a SAM- and H3K4-dependent manner []. Moreover, KMT2B plays a critical role in memory formation by mediating hippocampal H3K4 di- and trimethylation []. It is also required for RNA polymerase II association and protection from DNA methylation at the MagohB CpG island promoter []. KMT2B contains a CxxC (x for any residue) zinc finger domain, three PHD fingers, this ePHD finger, two FY (phenylalanine tyrosine)-rich domains, and a SET (Suppressor of variegation, Enhancer of zeste, Trithorax) domain.
