title: Purification, cloning, and characterization of XendoU, a novel endoribonuclease involved in processing of intron-encoded small nucleolar RNAs in Xenopus laevis.
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.
authors.affiliation: Institute Pasteur Fondazione Cenci-Bolognetti, Department of Genetics and Molecular Biology, University La Sapienza Piazzale Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Laneve
authors.forename: Fabio
authors.initials: F
authors.lastname: Altieri
authors.forename: Micol E
authors.initials: ME
authors.lastname: Fiori
authors.forename: Andrea
authors.initials: A
authors.lastname: Scaloni
authors.forename: Irene
authors.initials: I
authors.lastname: Bozzoni
authors.forename: Elisa
authors.initials: E
authors.lastname: Caffarelli
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002466:Cell Nucleolus / Q000235:genetics; D002467:Cell Nucleus / Q000201:enzymology; D002845:Chromatography; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D017886:Durapatite; D004625:Embryo, Nonmammalian; D004722:Endoribonucleases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D005260:Female; D007438:Introns; D008969:Molecular Sequence Data; D009865:Oocytes / Q000201:enzymology; D010446:Peptide Fragments / Q000737:chemistry; D012342:RNA, Small Nuclear / Q000235:genetics*; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D018076:DNA, Complementary; D010446:Peptide Fragments; D012342:RNA, Small Nuclear; D029867:Xenopus Proteins; D017886:Durapatite; D004722:Endoribonucleases; C475059:ENDOU protein, Xenopus