Extended PHD finger found in histone-lysine N-methyltransferase 2A (KMT2A) and 2B (KMT2B)
The extended plant homeodomain (ePHD) zinc finger is characterized as Cys2HisCys5HisCys2His. This subfamily includes the ePHD finger of histone-lysine N-methyltransferase trithorax (Trx) like proteins, KMT2A/MLL1 and KMT2B/MLL2. KMT2A and KMT2B comprise the mammalian Trx branch of COMPASS family, and are both essential for mammalian embryonic development. KMT2A 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. KMT2B is a second human homolog of Drosophila trithorax, located on chromosome 19 and functions as the catalytic subunit in the MLL2 complex. It 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. Both KMT2A and KMT2B contain a CxxC (x for any residue) zinc finger domain, three PHD fingers, this extended PHD (ePHD) finger, two FY (phenylalanine tyrosine)-rich domains, and a SET (Suppressor of variegation, Enhancer of zeste, Trithorax) domain.
Conserved feature residue pattern:C C H C C C C C H C C H
Evidence:
Comment:based on the structure evidence that human Borjeson-Forssman-Lehmann syndrome-associated protein PHF6 (PDB 4NN2) binds three Zn2+ ions through its ePHD finger
Comment:The extended PHD finger is characterized by Cys2HisCys5HisCys2His.
Jiyao W et al.(2023). "The conserved domain database in 2023.",