Evidence that homologous X-chromosome pairing requires transcription and Ctcf protein

Nat Genet. 2007 Nov;39(11):1390-6. doi: 10.1038/ng.2007.5. Epub 2007 Oct 21.

Abstract

X-chromosome inactivation (XCI) ensures the equality of X-chromosome dosages in male and female mammals by silencing one X in the female. To achieve the mutually exclusive designation of active X (Xa) and inactive X (Xi), the process necessitates that two Xs communicate in trans through homologous pairing. Pairing depends on a 15-kb region within the genes Tsix and Xite. Here, we dissect molecular requirements and find that pairing can be recapitulated by 1- to 2-kb subfragments of Tsix or Xite with little sequence similarity. However, a common denominator among them is the presence of the protein Ctcf, a chromatin insulator that we find to be essential for pairing. By contrast, the Ctcf-interacting partner, Yy1 (ref. 8), is not required. Pairing also depends on transcription. Transcriptional inhibition prevents new pair formation but does not perturb existing pairs. The kinetics suggest a pairing half-life of <1 h. We propose that pairing requires Ctcf binding and co-transcriptional activity of Tsix and Xite.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Blastocyst / cytology
  • CCCTC-Binding Factor
  • Cell Differentiation
  • Chromosomes, Mammalian / genetics*
  • DNA / metabolism
  • DNA-Binding Proteins / antagonists & inhibitors
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / metabolism
  • Embryo, Mammalian / cytology
  • Embryo, Mammalian / metabolism
  • Embryonic Stem Cells / cytology
  • Female
  • Gene Dosage
  • Humans
  • In Situ Hybridization, Fluorescence
  • Male
  • Mice
  • Mice, Transgenic
  • Molecular Sequence Data
  • Protein Binding
  • RNA, Long Noncoding
  • RNA, Small Interfering / pharmacology
  • RNA, Untranslated / genetics
  • RNA, Untranslated / metabolism
  • Repressor Proteins / antagonists & inhibitors
  • Repressor Proteins / genetics*
  • Repressor Proteins / metabolism
  • Trans-Activators / metabolism
  • Transcription, Genetic*
  • X Chromosome / genetics*
  • X Chromosome Inactivation / physiology*
  • YY1 Transcription Factor / genetics
  • YY1 Transcription Factor / metabolism
  • Zinc Fingers

Substances

  • CCCTC-Binding Factor
  • CTCF protein, human
  • Ctcf protein, mouse
  • DNA-Binding Proteins
  • RNA, Long Noncoding
  • RNA, Small Interfering
  • RNA, Untranslated
  • Repressor Proteins
  • Trans-Activators
  • Tsix transcript, mouse
  • YY1 Transcription Factor
  • Yy1 protein, mouse
  • DNA