Lysine-specific demethylase 5A is an enzyme that in humans is encoded by the KDM5A gene. The protein encoded by this gene is a ubiquitously expressed nuclear protein. It binds directly, with several other proteins, to retinoblastoma protein which regulates cell proliferation. It was formerly known as Retinoblastoma Binding Protein 2 (RBP2). This protein also interacts with rhombotin-2 which functions distinctly in erythropoiesis and in T-cell leukemogenesis. Rhombotin-2 is thought to either directly affect the activity of the encoded protein or may indirectly modulate the functions of the retinoblastoma protein by binding to this protein. Alternatively spliced transcript variants encoding distinct isoforms have been found for this gene. The Drosophila homolog, LID, was found to be an H3K4 histone demethylase that binds to c-Myc. It was recently renamed to Lysine Demethylase 5 (KDM5). Enzymatically can be designated as a trimethyllysine dioxygenase, which is a member of the alpha-ketoglutarate-dependent hydroxylase superfamily (EC 1.14.11.8).