title: Conserved core structure in the internal transcribed spacer 1 of the Schizosaccharomyces pombe precursor ribosomal RNA.
abstract: The structure of the internal transcribed spacer 1 (ITS1) in Schizosaccharomyces pombe was examined with respect to phylogenetically conserved features in yeasts as well as the binding of transacting factors that potentially play a role in ribosomal maturation. Computer analyses and probes for nuclease protection indicate a compact, more highly organized structure than previously proposed in Saccharomyces cerevisiae, with distinct structural features which can be recognized in S. cerevisiae. These include a central extended hairpin structure as well as smaller hairpins immediately adjacent to the maturing termini. Comparisons with ITS sequences in more diverse organisms indicate that the same features also can be recognized. This is especially clear in organisms which contain very short sequences in which the putative structures are much less ambiguous. Again nuclease protection analyses in one of these, Verticillium albo-atrum, confirm a central hairpin with additional hairpins linked to the maturing termini. Protein binding and gel retardation studies with the S. pombe ITS1 further indicate that, as observed in the 3' external transcripted spacer (ETS) region, the extended hairpin is not only the site of intermediate RNA cleavage during rRNA processing, but also a site for specific interactions with one or more soluble factors. Taken together with other analyses on transcribed spacer regions, the present data provide evidence that the spacer regions act not only to organize the maturing terminal sequences but also may serve to organize specific soluble factors, possibly acting in a manner which is analogous with that of the free small nucleolar ribonucleo protein particles (snoRNPs).
authors.affiliation: Department of Molecular Biology and Genetics, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
authors.forename: A I
authors.initials: AI
authors.lastname: Lalev
authors.forename: R N
authors.initials: RN
authors.lastname: Nazar
mesh_terms: D000818:Animals; D001483:Base Sequence; D001667:Binding, Competitive; D017124:Conserved Sequence; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D005656:Fungal Proteins / Q000378:metabolism; D008099:Liver / Q000166:cytology; D051379:Mice; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009698:Nucleoproteins / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D012322:RNA Precursors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012331:RNA, Fungal / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012335:RNA, Ribosomal / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D015719:Single-Strand Specific DNA and RNA Endonucleases / Q000378:metabolism; D014158:Transcription, Genetic; D014764:Viral Proteins
chemical_list: D005656:Fungal Proteins; D009698:Nucleoproteins; D012322:RNA Precursors; D012331:RNA, Fungal; D012335:RNA, Ribosomal; D014764:Viral Proteins; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases; D015719:Single-Strand Specific DNA and RNA Endonucleases