module: dmel_small_nucleolar_rnps
title: Small nucleolar ribonucleoprotein complexes in Drosophila melanogaster
label: snoRNPs
module_type: PROTEIN_COMPLEX
description: >-
  Small nucleolar ribonucleoproteins (snoRNPs) guide chemical modification and
  processing of ribosomal RNA in the nucleolus. Box H/ACA snoRNPs contain a guide
  RNA and four core proteins, the pseudouridine synthase dyskerin (Nop60B in
  Drosophila), Gar1, Nhp2 and Nop10, and convert target uridines into
  pseudouridine. Box C/D snoRNPs contain the methyltransferase fibrillarin with
  Nop56, Nop58 and a 15.5K protein and catalyse 2'-O-methylation of target
  nucleotides. The U3 box C/D snoRNP instead acts in early pre-rRNA cleavage
  within the small-subunit processome.
summary: >-
  Box H/ACA (pseudouridylation) and box C/D (2'-O-methylation) snoRNP protein
  cores.
concepts:
  - {id: GO:0005732, label: sno(s)RNA-containing ribonucleoprotein complex}
cellular_components:
  - {id: GO:0005730, label: nucleolus}
parts:
  - id: h_aca_snornp
    label: Box H/ACA snoRNP core
    role: rRNA pseudouridylation
    group: H-ACA
    complex_term: {id: GO:0031429, label: box H/ACA snoRNP complex}
    unit_functions:
      Nop60B: {id: GO:0009982, label: pseudouridine synthase activity}
    processes:
      - {id: GO:0031118, label: rRNA pseudouridine synthesis}
  - id: c_d_snornp
    label: Box C/D snoRNP proteins
    role: rRNA 2'-O-methylation and U3-dependent processing
    group: C-DRNP
    complex_term: {id: GO:0170049, label: box C/D RNP complex}
    unit_functions:
      Fib: {id: GO:0008649, label: rRNA methyltransferase activity}
    processes:
      - {id: GO:0000451, label: rRNA 2'-O-methylation}
notes: >-
  Parts follow FlyBase subgroups H-ACA and C-DRNP. The C/D group includes
  U3-55K, a U3 snoRNP-specific protein, so the part uses the general box C/D RNP
  complex term rather than the methylation-guide snoRNP term. The 15.5K core
  protein of C/D snoRNPs and the snoRNAs themselves are not in the FlyBase groups
  and are not participants. Nop60B has also been studied as minifly (mfl).