Xist

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Xist is an RNA gene on the X chromosome of the placental mammals that acts as major effector of the X inactivation process.

The Xist RNA, a large (17 kb in humans)[1] transcript, is expressed on the inactive chromosome and not on the active one. It is processed similarly to mRNAs, through splicing and polyadenylation, however, it remains untranslated. It has been suggested that this RNA gene evolved at least partly from a protein coding gene that became a pseudogene.[2]

The inactive X is coated with this transcript, which is essential for the inactivation. X lacking Xist will not be inactivated, while duplication of the Xist gene on another chromosome causes inactivation of that chromosome.

[edit] References

  1. ^ Brown CJ, Hendrich BD, Rupert JL, et al (1992). "The human XIST gene: analysis of a 17 kb inactive X-specific RNA that contains conserved repeats and is highly localized within the nucleus". Cell 71 (3): 527–42. PMID 1423611. 
  2. ^ Duret L, Chureau C, Samain S, Weissenbach J, Avner P (2006). "The Xist RNA gene evolved in eutherians by pseudogenization of a protein-coding gene". Science 312 (5780): 1653–5. doi:10.1126/science.1126316. PMID 16778056. 

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