Journal Article

Characterization and quantitation of differential <i>Tsix</i> transcripts: implications for <i>Tsix</i> function

Shinwa Shibata and Jeannie T. Lee

in Human Molecular Genetics

Volume 12, issue 2, pages 125-136
Published in print January 2003 | ISSN: 0964-6906
Published online January 2003 | e-ISSN: 1460-2083 | DOI:
Characterization and quantitation of differential Tsix transcripts: implications for Tsix function

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In dosage compensation of female mammals, the accumulation of Xist RNA initiates silencing of one X-chromosome. Xist action is repressed by the antisense gene, Tsix, whose full-length RNA product is complementary to Xist RNA in mice. While previous work showed that Tsix transcription blocks the accumulation of Xist RNA, it is still unclear whether this repression requires the antisense RNA product or whether the antisense transcriptional movement is sufficient. A better understanding of potential mechanisms requires elucidation of Tsix RNA structure and determination of Tsix RNA copy number relative to that of Xist RNA. Previous work indicated that at least some of murine Tsix is spliced and that human TSIX truncates within the 3′ end of XIST. Here, further characterization and quantitation of murine Tsix RNA reveal three new findings: first, in undifferentiated embryonic stem cells, Tsix RNA is present at 10–100-fold molar excess over Xist RNA. Second, only 30–60% of Tsix RNA is spliced at known exon–intron junctions. The nearly equal abundance of spliced and unspliced species leaves open possible roles for both isoforms. Finally, Tsix is spliced heterogeneously at the 5′ end and most detectable splice variants exhibit only a 1.9 kb region of complementarity between sense and antisense RNAs. Implications for Tsix's possible mechanisms of action are discussed.

Journal Article.  8809 words.  Illustrated.

Subjects: Genetics and Genomics

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