The UTX gene escapes X inactivation in mice and humans

We recently have identified a ubiquitously transcribed mouse Y chromosomegene, Uty , which encodes a tetratricopeptide repeat (TPR) protein. Apeptide derived from the UTY protein confers H-Y antigenicity on malecells. Here we report the characterization of a widely transcribed X-linkedhomologue of Uty , called Utx , which maps to the proximal region of themouse X chromosome and which detects a human X-linked homologue at Xp11.2.Given that Uty is ubiquitously transcribed, we assayed for Utx expressionfrom the inactive X chromosome (Xi) in mice and found that Utx escapes Xchromosome inactivation. Only Smcx and the pseudoautosomal Sts gene on themouse X chromosome have been reported previously to escape inactivation.The human UTX gene was also found to be expressed from Xi. We discuss thesignificance of these data for our understanding of dosage compensation ofX-Y homologous genes in humans and mice.