title: Depletion of the yeast nuclear exosome subunit Rrp6 results in accumulation of polyadenylated RNAs in a discrete domain within the nucleolus.
abstract: Recent data reveal that a substantial fraction of transcripts generated by RNA polymerases I, II, and III are rapidly degraded in the nucleus by the combined action of the exosome and a noncanonical poly(A) polymerase activity. This work identifies a domain within the yeast nucleolus that is enriched in polyadenylated RNAs in the absence of the nuclear exosome RNase Rrp6 or the exosome cofactor Mtr4. In normal yeast cells, poly(A)(+) RNA was undetectable in the nucleolus but the depletion of either Rrp6 or Mtr4 led to the accumulation of polyadenylated RNAs in a discrete subnucleolar region. This nucleolar poly(A) domain is enriched for the U14 snoRNA and the snoRNP protein Nop1 but is distinct from the nucleolar body that functions in snoRNA maturation. In strains lacking both Rrp6 and the poly(A) polymerase Trf4, the accumulation of poly(A)(+) RNA was suppressed, suggesting the involvement of the Trf4-Air1/2-Mtr4 polyadenylation (TRAMP) complex. The accumulation of polyadenylated snoRNAs in a discrete nucleolar domain may promote their recognition as substrates for the exosome.
authors.affiliation: Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisbon, Portugal.
authors.forename: Tiago
authors.initials: T
authors.lastname: Carneiro
authors.forename: Célia
authors.initials: C
authors.lastname: Carvalho
authors.forename: José
authors.initials: J
authors.lastname: Braga
authors.forename: José
authors.initials: J
authors.lastname: Rino
authors.forename: Laura
authors.initials: L
authors.lastname: Milligan
authors.forename: David
authors.initials: D
authors.lastname: Tollervey
authors.forename: Maria
authors.initials: M
authors.lastname: Carmo-Fonseca
mesh_terms: D002466:Cell Nucleolus / Q000378:metabolism / Q000648:ultrastructure; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D005095:Exoribonucleases / Q000235:genetics / Q000378:metabolism*; D063326:Exosome Multienzyme Ribonuclease Complex; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D011062:Polynucleotide Adenylyltransferase / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D020537:RNA, Small Nucleolar / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020718:Ribonucleoproteins, Small Nucleolar / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C064793:NOP1 protein, S cerevisiae; D009687:Nuclear Proteins; D021122:Protein Subunits; D012333:RNA, Messenger; D020537:RNA, Small Nucleolar; D011993:Recombinant Fusion Proteins; D020718:Ribonucleoproteins, Small Nucleolar; D029701:Saccharomyces cerevisiae Proteins; C429559:PAP1 protein, S cerevisiae; D011062:Polynucleotide Adenylyltransferase; D004259:DNA-Directed DNA Polymerase; C487545:PAP2 protein, S cerevisiae; D005095:Exoribonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; C112610:RRP6 protein, S cerevisiae; C101004:MTR4 protein, S cerevisiae; D053487:DEAD-box RNA Helicases