title: Identification of protein factors and U3 snoRNAs from a Brassica oleracea RNP complex involved in the processing of pre-rRNA.
abstract: We report on the structural characterization of a functional U3 snoRNA ribonucleoprotein complex isolated from Brassica oleracea. The BoU3 snoRNP complex (formerly NF D) binds ribosomal DNA (rDNA), specifically cleaves pre-rRNA at the primary cleavage site in vitro and probably links transcription to early pre-rRNA processing in vivo. Using a proteomic approach we have identified 62 proteins in the purified BoU3 snoRNP fraction, including small RNA associated proteins (Fibrillarin, NOP5/Nop58p, Diskerin/Cbf5p, SUS2/PRP8 and CLO/GFA1/sn114p) and 40S ribosomal associated proteins (22 RPS and four ARCA-like proteins). Another major protein group is composed of chaperones/chaperonins (HSP81/TCP-1) and at least one proteasome subunit (RPN1a). Remarkably, RNA-dependent RNA polymerase (RdRP) and Tudor staphylococcal nuclease (TSN) proteins, which have RNA- and/or DNA-associated activities, were also revealed in the complex. Furthermore, three U3 snoRNA variants were identified in the BoU3 snoRNP fraction, notably an evolutionarily conserved and variable stem loop structure located just downstream from the C-box domain of the U3 sequence structures. We conclude that the BoU3 snoRNP complex is mainly required for 40S pre-ribosome synthesis. It is also expected that U3 snoRNA variants and interacting proteins might play a major role in BoU3 snoRNP complex assembly and/or function. This study provides a basis for further investigation of these novel ribonucleoprotein factors and their role in plant ribosome biogenesis.
authors.affiliation: Laboratoire Génome et Développement des Plantes, UMR 5096 CNRS-IRD-UPVD, Perpignan France.
authors.forename: Hala
authors.initials: H
authors.lastname: Samaha
authors.forename: Valérie
authors.initials: V
authors.lastname: Delorme
authors.forename: Frederic
authors.initials: F
authors.lastname: Pontvianne
authors.forename: Richard
authors.initials: R
authors.lastname: Cooke
authors.forename: Francois
authors.initials: F
authors.lastname: Delalande
authors.forename: Alain
authors.initials: A
authors.lastname: Van Dorsselaer
authors.forename: Manuel
authors.initials: M
authors.lastname: Echeverria
authors.forename: Julio
authors.initials: J
authors.lastname: Sáez-Vásquez
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001937:Brassica / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D017124:Conserved Sequence; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D012322:RNA Precursors / Q000378:metabolism*; D020537:RNA, Small Nucleolar / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000737:chemistry / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: D010940:Plant Proteins; D012322:RNA Precursors; D020537:RNA, Small Nucleolar; C117378:RNA, U3 small nucleolar; D012261:Ribonucleoproteins