Sensing X chromosome pairs before X inactivation via a novel X-pairing region of the Xic.
Mammalian dosage compensation involves silencing of one of the two X chromosomes in females and is controlled by the X-inactivation center (Xic). The Xic, which includes Xist and its antisense transcription unit Tsix/Xite, somehow senses the number of X chromosomes and triggers Xist up-regulation from one of the two X chromosomes in females. We found that a segment of the mouse Xic lying several hundred kilobases upstream of Xist brings the two Xics together before the onset of X inactivation. This region can autonomously drive Xic trans-interactions even as an ectopic single-copy transgene. Its introduction into male embryonic stem cells is strongly selected against, consistent with a possible role in trans-activating Xist. We propose that homologous associations driven by this novel X-pairing region (Xpr) of the Xic enable a cell to sense that more than one X chromosome is present and coordinate reciprocal Xist/Tsix expression.
CNRS UMR218, Curie Institute, 26 rue d'Ulm, Paris 75005, France.
S
S
Augui
G J
GJ
Filion
S
S
Huart
E
E
Nora
M
M
Guggiari
M
M
Maresca
A F
AF
Stewart
E
E
Heard
D000483:Alleles; D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D023902:Chromosome Pairing; D022202:Chromosomes, Artificial, Bacterial; D015536:Down-Regulation; D053595:Embryonic Stem Cells; D005260:Female; D051379:Mice; D008822:Mice, Transgenic; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics / Q000378:metabolism; D016196:S Phase; D014162:Transfection; D019076:Transgenes; D015854:Up-Regulation; D014960:X Chromosome / Q000235:genetics* / Q000502:physiology; D049951:X Chromosome Inactivation
D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; C465658:Tsix transcript, mouse; C077885:XIST non-coding RNA