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Transient Homologous Chromosome Pairing Marks the Onset of X Inactivation
Na Xu,Chia-Lun Tsai,Jeannie T. Lee*
Mammalian X inactivation turns off one female X chromosome toenact dosage compensation between XX and XY individuals. X inactivationis known to be regulated in cis by Xite, Tsix, and Xist, butin principle the two Xs must also be regulated in trans to ensuremutually exclusive silencing. Here, we demonstrate that interchromosomalpairing mediates this communication. Pairing occurs transientlyat the onset of X inactivation and is specific to the X-inactivationcenter. Deleting Xite and Tsix perturbs pairing and counting/choice,whereas their autosomal insertion induces de novo X-autosomepairing. Ectopic X-autosome interactions inhibit endogenousX-X pairing and block the initiation of X-chromosome inactivation.Thus, Tsix and Xite function both in cis and in trans. We proposethat Tsix and Xite regulate counting and mutually exclusivechoice through X-X pairing.
Howard Hughes Medical Institute, Department of Molecular Biology, Massachusetts General Hospital, Department of Genetics, Harvard Medical School Boston, MA 02114, USA.
* To whom correspondence should be addressed. E-mail: lee{at}molbio.mgh.harvard.edu
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Genetics
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|Abstract »|Full Text »|PDF »
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|Abstract »|Full Text »|PDF »
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