3 GENES THAT ESCAPE X-CHROMOSOME INACTIVATION ARE CLUSTERED WITH A 6-MB YAC-CONTIG AND STS MAP IN XP11.21-P11.22

In order to study the distribution of genes that escape X chromosome i nactivation, a high density yeast artificial chromosome (YAC) contig a nd STS map spanning approximately 6 Mb has been constructed in Xp11.21 -p11.22. The contig contains 113 YACs mapped with 53 markers, includin g 10 genes. Four genes have been assayed for their expression status o n both the active and inactive human X chromosomes, and these data hav e been combined with previous results on two other genes in the contig . Three of these genes escape X inactivation and have been localized t o a single YAC clone of similar to 1075 kb. The other three genes are subject to inactivation, with two of them lying among the genes that e scape inactivation. These results suggest that there are both regional control signals as well as gene-specific elements that determine the X inactivation status of genes on the proximal short arm of the human X chromosome.