module: dmel_rna_exosome
title: RNA exosome and nuclear exosome targeting complex in Drosophila melanogaster
label: RNA exosome
module_type: PROTEIN_COMPLEX
description: >-
  The RNA exosome is a 3'-5' exoribonuclease complex that processes and degrades
  many classes of RNA in the nucleus and cytoplasm. A catalytically inactive
  nine-subunit barrel, made of a six-subunit ring (including Ski6, Mtr3, Rrp42,
  Rrp45 and Rrp46) capped by Csl4, Rrp4 and Rrp40, channels RNA to the
  processive exonuclease and endonuclease Dis3 (Rrp44). The nuclear exosome
  also contains the distributive exonuclease Rrp6. Nuclear cofactors deliver
  substrates: the nuclear exosome targeting (NEXT) complex, formed by the RNA
  helicase Mtr4, a zinc-knuckle protein (CG4622, ZCCHC8 homolog) and an RRM
  protein (CG11454, RBM7 homolog), targets short-lived non-polyadenylated
  transcripts for decay.
summary: >-
  Nine-subunit exosome barrel with Dis3 and Rrp6 exonucleases, and the NEXT
  complex that targets nuclear transcripts to it.
concepts:
  - {id: GO:0000178, label: exosome (RNase complex)}
cellular_components:
  - {id: GO:0005634, label: nucleus}
  - {id: GO:0005737, label: cytoplasm}
parts:
  - id: exosome_core
    label: Exosome nine-subunit core
    role: RNA-channelling barrel
    genes: [Csl4, Rrp4, Rrp40, Rrp42, Rrp45, Rrp46, Mtr3, Ski6]
    complex_term: {id: GO:0000178, label: exosome (RNase complex)}
  - id: exosome_nucleases
    label: Exosome-associated ribonucleases
    role: catalytic subunits
    description: >-
      Dis3 is present in both nuclear and cytoplasmic exosomes; Rrp6 is
      nuclear.
    genes: [Dis3, Rrp6]
    complex: false
    function: {id: GO:0000175, label: 3'-5'-RNA exonuclease activity}
  - id: next_complex
    label: Nuclear exosome targeting complex
    role: nuclear substrate delivery
    group: NEXT
    complex_term: {id: GO:0062141, label: nuclear exosome targeting complex}
    unit_functions:
      Mtr4: {id: GO:0003724, label: RNA helicase activity}
    processes:
      - {id: GO:0071027, label: nuclear RNA surveillance}
connections:
  - {source: next_complex, target: exosome_nucleases, connection_type: PROVIDES_INPUT_FOR, description: NEXT unwinds and delivers nuclear RNA substrates to the exosome.}
notes: >-
  Boundary. FlyBase groups the nuclear exosome (RNA-EXO, with Rrp6) and the
  cytoplasmic exosome (RNA-EXOC, without Rrp6); both are captured by the
  shared core and nuclease parts, with Rrp6's nuclear restriction noted. The
  Ski complex, TRAMP and other cytoplasmic and nuclear cofactors have no
  FlyBase group here and are not added.