Functional Characterization of XendoU, the Endoribonuclease Involved in Small Nucleolar RNA Biosynthesis

• Published in: The Journal of biological chemistry 2005-05, Vol.280 (19), p.18996-19002
• Main Authors: Gioia, Ubaldo, Laneve, Pietro, Dlakić, Mensur, Arceci, Massimo, Bozzoni, Irene, Caffarelli, Elisa
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Catalysis; Catalytic Domain; Cloning, Molecular; DNA Primers - chemistry; Endoribonucleases - chemistry; Endoribonucleases - physiology; Glutamic Acid - chemistry; Histidine - chemistry; Introns; Lysine - chemistry; Manganese - chemistry; Molecular Sequence Data; Mutation; Oligopeptides - chemistry; Phylogeny; Plasmids - metabolism; Protein Binding; Protein Structure, Tertiary; Recombinant Proteins - chemistry; RNA, Small Nuclear - metabolism; Sequence Homology, Amino Acid; Substrate Specificity; Transcription, Genetic; Xenopus; Xenopus laevis; Xenopus Proteins - chemistry; Xenopus Proteins - physiology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M501160200

XendoU is the endoribonuclease involved in the biosynthesis of a specific subclass of Xenopus laevis intron-encoded small nucleolar RNAs. XendoU has no homology to any known cellular RNase, although it has sequence similarity with proteins tentatively annotated as serine proteases. It has been recently shown that XendoU represents the cellular counterpart of a nidovirus replicative endoribonuclease (NendoU), which plays a critical role in viral replication and transcription. In this paper, we combined prediction and experimental data to define the amino acid residues directly involved in XendoU catalysis. Specifically, we find that XendoU residues Glu-161, Glu-167, His-162, His-178, and Lys-224 are essential for RNA cleavage, which occurs in the presence of manganese ions. Furthermore, we identified the RNA sequence required for XendoU binding and showed that the formation of XendoU-RNA complex is Mn2+-independent.