title: RAC protein directs the complete removal of the 3' external transcribed spacer by the Pac1 nuclease.
abstract: In Schizosaccharomyces pombe, interdependency in rRNA processing is mediated by a large protein complex (RAC) which contains independent binding sites for each of the transcribed spacers. The RAC complex exhibits no nuclease activity but dramatically alters the efficiency and specificity of the Pac1 nuclease, leading to the complete removal of the 3' ETS. Furthermore, the affinity of RAC protein for mutant 3' ETS correlates closely with in vivo effects on rRNA processing, and changes which disrupt RAC protein binding also inhibit Pac1 nuclease cleavage at the 3' end of the 25S rRNA sequence. The observations indicate that, in the presence of the RAC protein/3' ETS complex, cleavage by the RNase III-like homolog is not restricted to the known intermediate sites but also is directed at the 3' end of the 25S rRNA.
authors.affiliation: Department of Molecular Biology and Genetics, University of Guelph, Ontario, Canada.
authors.forename: Krasimir
authors.initials: K
authors.lastname: Spasov
authors.forename: Liliana I
authors.initials: LI
authors.lastname: Perdomo
authors.forename: Eugeni
authors.initials: E
authors.lastname: Evakine
authors.forename: Ross N
authors.initials: RN
authors.lastname: Nazar
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D004271:DNA, Fungal / Q000378:metabolism*; D021903:DNA, Ribosomal Spacer / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D004722:Endoribonucleases / Q000378:metabolism*; D005656:Fungal Proteins; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D012322:RNA Precursors / Q000378:metabolism*; D012331:RNA, Fungal / Q000096:biosynthesis*; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D012568:Schizosaccharomyces / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000502:physiology*; D020744:rac GTP-Binding Proteins / Q000502:physiology*
chemical_list: D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer; D005656:Fungal Proteins; D012322:RNA Precursors; D012331:RNA, Fungal; D012335:RNA, Ribosomal; D029702:Schizosaccharomyces pombe Proteins; C065039:RNA, ribosomal, 25S; D004722:Endoribonucleases; C499540:pac1 protein, S pombe; D020744:rac GTP-Binding Proteins