title: Pac1 endonuclease and Dhp1p 5'-->3' exonuclease are required for U3 snoRNA termination in Schizosaccharomyces pombe.
abstract: Maturation of some snoRNAs is dependent on RNase III-like endonuclease-mediated transcript cleavage, which serves as an entry for the nuclear exosome complex that trims the transcript at the 3'-end. Sequence deletions suggest this cleavage in the U3 snoRNA transcripts of Schizosaccharomyces pombe can induce transcript termination. Using mutational analyses, we demonstrate that the degree of cleavage correlates closely with both RNA maturation and transcript termination. We also show that the RNase III-like endonuclease, Pac1, and the nuclear 5'-exonuclease, Dhp1p, are essential for RNA production and transcript termination, supporting a "reversed torpedoes" model in which the endonuclease cut allows 5'- and 3'-exonuclease activities access to the transcript, leading simultaneously to transcript termination in one direction and RNA maturation in the other.
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
authors.forename: Sadeq
authors.initials: S
authors.lastname: Nabavi
authors.forename: Ross N
authors.initials: RN
authors.lastname: Nazar
mesh_terms: D047369:Chromatin Immunoprecipitation; D004722:Endoribonucleases / Q000378:metabolism*; D005095:Exoribonucleases / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics*; D020537:RNA, Small Nucleolar / Q000235:genetics*; D012568:Schizosaccharomyces / Q000201:enzymology* / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D004722:Endoribonucleases; D005095:Exoribonucleases; D020537:RNA, Small Nucleolar; D029702:Schizosaccharomyces pombe Proteins; C117378:RNA, U3 small nucleolar; C087281:dhp1 protein, S pombe; C499540:pac1 protein, S pombe