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Science 24 February 2006:
Vol. 311. no. 5764, p. 1068
DOI: 10.1126/science.311.5764.1068m
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This Week in Science

In mammals, females have two X chromosomes and males have only one. Potentially lethal X-chromosome gene imbalance is prevented by dosage compensation, where one of the two X chromosomes in female cells is inactivated (Xi) while the other remains active (Xa). Silencing of the "supernumerary X" chromosome in females is regulated by the X-inactivation center (Xic) on the X chromosome. The mutually exclusive nature of the Xa/Xi choice suggests that there must be some form of communication between the two X chromosomes. Xu et al. (p. 1149, published online 19 January; see the Perspective by Carrel) now show that in mouse cells undergoing dosage compensation and X inactivation, such communication takes the form of a transient physical interaction between the Xic of the two X chromosomes. Placing additional copies of the Xic on autosomes induces ectopic X-autosome interactions which interfere with the normal process of X-chromosome inactivation.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)