Purification,cloning, and characterization of XendoU,a novel endoribonuclease involved in processing of intron-encoded small nucleolar RNAs in Xenopus laevis |
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Authors: | Laneve Pietro Altieri Fabio Fiori Micol E Scaloni Andrea Bozzoni Irene Caffarelli Elisa |
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Affiliation: | Institute Pasteur Fondazione Cenci-Bolognetti, Department of Genetics and Molecular Biology, University La Sapienza Piazzale Aldo Moro 5, 00185 Rome, Italy. |
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Abstract: | Here we report the purification, from Xenopus laevis oocyte nuclear extracts, of a new endoribonuclease, XendoU, that is involved in the processing of the intron-encoded box C/D U16 small nucleolar RNA (snoRNA) from its host pre-mRNA. Such an activity has never been reported before and has several uncommon features that make it quite a novel enzyme: it is poly(U)-specific, it requires Mn(2+) ions, and it produces molecules with 2'-3'-cyclic phosphate termini. Even if XendoU cleaves U-stretches, it displays some preferential cleavage on snoRNA precursor molecules. XendoU also participates in the biosynthesis of another intron-encoded snoRNA, U86, which is contained in the NOP56 gene of Xenopus laevis. A common feature of these snoRNAs is that their production is alternative to that of the mRNA, suggesting an important regulatory role for all the factors involved in the processing reaction. |
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