title: A small nucleolar RNA is processed from an intron of the human gene encoding ribosomal protein S3.
abstract: A human small nucleolar RNA, identified previously in HeLa cells by anti-fibrillarin autoantibody precipitation and termed RNA X, has been characterized. It comprises two uridine-rich variants (148 and 146 nucleotides), which we refer to as snRNA U15A and U15B. Secondary structure models predict for both variants a U15-specific stem-loop structure, as well as a new structural motif that contains conserved sequences and can also be recognized in the other fibrillarin-associated nucleolar snRNAs, U3, U14, and RNA Y. The single-copy gene for human U15A has been found unexpectedly to reside in intron 1 of the ribosomal protein S3 gene; the U15A sequence appears on the same strand as the S3 mRNA and does not exhibit canonical transcription signals for nuclear RNA polymerases. U15A RNA is processed in vitro from S3 intron 1 transcripts to yield the correct 5' end with a 5'-monophosphate; the in vitro system requires ATP for 3' cleavage, which occurs a few nucleotides downstream of the mature end. The production of a single primary transcript specifying the mRNA for a ribosomal or nucleolar protein and a nucleolar snRNA may constitute a general mechanism for balancing the levels of nucleolar components in vertebrate cells.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06536-0812.
authors.forename: K T
authors.initials: KT
authors.lastname: Tycowski
authors.forename: M D
authors.initials: MD
authors.lastname: Shu
authors.forename: J A
authors.initials: JA
authors.lastname: Steitz
mesh_terms: D001483:Base Sequence; D002466:Cell Nucleolus / Q000737:chemistry*; D002474:Cell-Free System; D017124:Conserved Sequence; D004591:Electrophoresis, Polyacrylamide Gel; D006367:HeLa Cells; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012322:RNA Precursors; D012323:RNA Processing, Post-Transcriptional; D012342:RNA, Small Nuclear / Q000737:chemistry* / Q000235:genetics*; D015183:Restriction Mapping; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics*; D017423:Sequence Analysis, RNA; D014500:Uracil Nucleotides / Q000032:analysis
chemical_list: D012322:RNA Precursors; D012342:RNA, Small Nuclear; D012269:Ribosomal Proteins; D014500:Uracil Nucleotides; C044152:ribosomal protein S3