JARID1A/RBP2 is a member of the jumonji (jmj) domain containing gene family of histone demethylases that plays a role in chromatin regulation and influences transcriptional activation and suppression. Some recently characterized members of the jmj family include JARID1A/RBP2, JARID1C, JMJD1A, JMJD1B, JMJD1C, JMJD2A, JMJD2C and JMJD2D. JARID1A/RBP2 functions to specifically demethylate lys-4 of histone 3 and interacts with the tumor suppressor protein pRb.