A dual origin of the Xist gene from a protein-coding gene and a set of transposable elements.
X-chromosome inactivation, which occurs in female eutherian mammals is controlled by a complex X-linked locus termed the X-inactivation center (XIC). Previously it was proposed that genes of the XIC evolved, at least in part, as a result of pseudogenization of protein-coding genes. In this study we show that the key XIC gene Xist, which displays fragmentary homology to a protein-coding gene Lnx3, emerged de novo in early eutherians by integration of mobile elements which gave rise to simple tandem repeats. The Xist gene promoter region and four out of ten exons found in eutherians retain homology to exons of the Lnx3 gene. The remaining six Xist exons including those with simple tandem repeats detectable in their structure have similarity to different transposable elements. Integration of mobile elements into Xist accompanies the overall evolution of the gene and presumably continues in contemporary eutherian species. Additionally we showed that the combination of remnants of protein-coding sequences and mobile elements is not unique to the Xist gene and is found in other XIC genes producing non-coding nuclear RNA.
Institute of Cytology and Genetics, Russian Academy of Sciences, Siberian Department, Novosibirsk, Russia.
Eugeny A
EA
Elisaphenko
Nikolay N
NN
Kolesnikov
Alexander I
AI
Shevchenko
Igor B
IB
Rogozin
Tatyana B
TB
Nesterova
Neil
N
Brockdorff
Suren M
SM
Zakian
D000818:Animals; D004251:DNA Transposable Elements; D005091:Exons; D005260:Female; D051379:Mice; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D020080:Tandem Repeat Sequences; D049951:X Chromosome Inactivation
D004251:DNA Transposable Elements; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; C077885:XIST non-coding RNA