The trithorax-group (trxG) protein Ash2 from C. elegans (or ASH2L in mammals) is a component of the Set1/Ash2 histone methyltransferase (HMT) complex that methylates 'Lys-4' of histone H3, a mark associated with epigenetic transcriptional activation [, ]. Mammals posses several SET1 family proteins (MLL1-4, SET1A, and SET1B). ASH2L is a core component of all the resulting mammalian histone H3K4 methyltransferase complexes, including mixed lineage leukemia (MLL) complexes [].S. cerevisiae Bre2 is homologous to Ash2 []. TRAUCO (TRO) is the homologue from Arabidopsis, which is required for early embryogenesis [].
The extended plant homeodomain (ePHD) zinc finger is characterized as Cys2HisCys5HisCys2His. This entry represents the ePHD finger of Histone-lysine N-methyltransferase 2A (KMT2A), which is a histone methyltransferase that belongs to the MLL subfamily of H3K4-specific histone lysine methyltransferases (KMT2). It regulates chromatin-mediated transcription through the catalysis of methylation of histone 3 lysine 4 (H3K4), and is frequently rearranged in acute leukemia []. KMT2A functions as the catalytic subunit in the MLL1 complex, which also contains WDR5, RbBP5, ASH2L and DPY30 as integral core subunits required for the efficient methylation activity of the complex [, ]. The MLL1 complex is highly active and specific for H3K4 methylation. KMT2A contains a CxxC (x for any residue) zinc finger domain, three PHD fingers, a Bromodomain domain, this extended PHD finger, two FY (phenylalanine tyrosine)-rich domains, and a SET (Suppressor of variegation, Enhancer of zeste, Trithorax) domain [].
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.
