PHD finger found in Arabidopsis thaliana histone-lysine N-methyltransferase arabidopsis trithorax-like protein ATX1, ATX2, and similar proteins
The family includes A. thaliana ATX1 and ATX2, both of which are sister paralogs originating from a segmental chromosomal duplication. They are plant counterparts of the Drosophila melanogaster trithorax (TRX) and mammalian mixed-lineage leukemia (MLL1) proteins. ATX1, also termed protein SET domain group 27, or trithorax-homolog protein 1 (TRX-homolog protein 1), is a methyltransferase that trimethylates histone H3 at lysine 4 (H3K4me3). It also acts as a histone modifier and as a positive effector of gene expression. ATX1regulates transcription from diverse classes of genes implicated in biotic and abiotic stress responses. It is involved in dehydration stress signaling in both abscisic acid (ABA)-dependent and ABA-independent pathways. ATX2, also termed protein SET domain group 30, or trithorax-homolog protein 2 (TRX-homolog protein 2), is involved in dimethylating histone H3 at lysine 4 (H3K4me2). Both ATX1 and ATX2 are multi-domain containing proteins that consist of an N-terminal PWWP domain, FYRN- and FYRC (DAST, domain associated with SET in trithorax) domains, a canonical Cys4HisCys3 plant homeodomain (PHD) finger, a non-canonical extended PHD (ePHD) finger, Cys2HisCys5HisCys2His, and a C-terminal SET domain; this model corresponds to the Cys4HisCys3 canonical PHD finger.
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