Human JMJD2A, also known as JHDM3A and KDM4A (GenBank Accession No. NM_014663), amino-acids 1-350 with N-terminal His-tag, MW=42 kDa, expressed in an E.coli expression system.

JMJD2A (Jumonji domain containing 2A) belongs to the conserved family of Jmjc domain-containing proteins, which in turn are a part of the Jmjc domain histone demethylase superfamily. JMJD2A protein is composed of 1064 amino acids, and contains JmjN and JmjC domains in the catalytic core, a linker region of 350 residues, two plant homeodomains (PHD), and a double Tudor domain. It is one of the six JMJD2 homologs found in humans, ranging from JMJD2A to JMJD2F. It is a trimethyllysine-specific JmjC histone demethylase (HDM).

JMJD2A (Jumonji domain containing 2A) acts as a repressor of transcription, and interacts with histone deacetylase complexes and Rb (retinoblastoma) protein. In histone H3, H3K9me2/3 and H3K36me2/3, this protein is responsible for the demethylation of di- and trimethylated Lys9 and Lys36 residues. It is up-regulated in breast cancer and is responsible for the transcriptional repression of the tumor suppressor ARHI (aplasia Ras homolog member I) which eventually promotes breast cancer proliferation, migration and invasion.