Xist (X-inactive specific transcript) is a non-coding RNA on the X chromosome of the placental mammals that acts as a major effector of the X-inactivation process. It is a component of the Xic – X-chromosome inactivation centre – along with two other RNA genes (Jpx and Ftx) and two protein genes (Tsx and Cnbp2). The human Xist gene was discovered by Andrea Ballabio through a cDNA library screening and then characterized in collaboration with Carolyn J. Brown and Hunt Willard.