Murine Xist RNA isoforms are different at their 3' ends: a role for differential polyadenylation.
Murine Xist is an essential transcript for X chromosome inactivation (X inactivation). According to recently revised structure, Xist is at least 17.8 kb long. It consists of seven exons and there are two major transcripts in female somatic cells. In this study we further defined the molecular structures of the two isoforms, namely short (S) and long (L) forms by northern blot and RNAse protection assay (RPA). The following lines of evidences suggest that mouse Xist depends on differential polyadenylation, not alternative splicing, to generate the two RNA isoforms: (1) only one band was detectable with the northern probes spanning the 3' end of Xist. (2) RPA showed the 3' termini of both S and L forms, and there are putative polyadenylation signals and hairpin structures close to these ends. (3) Analyses by splice site prediction program did not show any evidence of splice motifs in the sequence of L form. (4) Alignments between Xist 3' end (ESTs) and genomic sequence support the absence of splicing event in the region. The newly revised structure of Xist isoforms may have different stability and roles in the process of X inactivation.
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Harvard Institute of Human Genetics, Harvard Medical School and Beth Israel Deaconess Medical Center, Room 441A, 4 Blackfan Circle, Boston, MA 02115, USA.
Hong
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YK
Kim
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DH
Ontiveros
S D
SD
Strauss
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WM
D000818:Animals; D015152:Blotting, Northern; D005260:Female; D007668:Kidney / Q000378:metabolism; D008297:Male; D051379:Mice; D011061:Poly A / Q000235:genetics; D012313:RNA / Q000235:genetics*; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic
D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D014157:Transcription Factors; C077885:XIST non-coding RNA; D011061:Poly A; D012313:RNA