module: dmel_nuclear_rna_polymerases
title: Nuclear DNA-directed RNA polymerases I, II and III in Drosophila melanogaster
label: Nuclear RNA polymerases
module_type: PROTEIN_COMPLEX
description: >-
  Eukaryotic nuclei contain three multisubunit DNA-directed RNA polymerases.
  RNA polymerase I transcribes the large ribosomal RNA precursor in the
  nucleolus, RNA polymerase II transcribes mRNAs and most snRNAs and
  microRNA precursors, and RNA polymerase III transcribes tRNAs, 5S rRNA, U6
  snRNA and other short structured RNAs. Each enzyme has two large catalytic
  subunits that form the active site, a set of subunits shared by all three
  enzymes (RPABC1, RPABC2, RPABC3, RPABC4 and RPABC5), subunits shared by Pol I
  and Pol III (RPAC1 and RPAC2), and enzyme-specific subunits.
summary: >-
  RNA polymerases I, II and III, which share five common subunits and
  transcribe rRNA, mRNA and short structured RNAs respectively.
concepts:
  - {id: GO:0055029, label: nuclear DNA-directed RNA polymerase complex}
cellular_components:
  - {id: GO:0005634, label: nucleus}
parts:
  - id: rna_polymerase_i
    label: RNA polymerase I
    role: rRNA transcription
    group: RNAPI
    complex_term: {id: GO:0005736, label: RNA polymerase I complex}
    function: {id: GO:0003899, label: DNA-directed RNA polymerase activity}
    processes:
      - {id: GO:0006360, label: transcription by RNA polymerase I}
  - id: rna_polymerase_ii
    label: RNA polymerase II
    role: mRNA and snRNA transcription
    group: RNAPII
    complex_term: {id: GO:0005665, label: "RNA polymerase II, core complex"}
    function: {id: GO:0003899, label: DNA-directed RNA polymerase activity}
    processes:
      - {id: GO:0006366, label: transcription by RNA polymerase II}
  - id: rna_polymerase_iii
    label: RNA polymerase III
    role: tRNA, 5S rRNA and short RNA transcription
    group: RNAPIII
    complex_term: {id: GO:0005666, label: RNA polymerase III complex}
    function: {id: GO:0003899, label: DNA-directed RNA polymerase activity}
    processes:
      - {id: GO:0006383, label: transcription by RNA polymerase III}
notes: >-
  Boundary. The common subunits (Polr2E, Polr2F, Polr2H, Polr2K, Polr2L) and
  the Pol I/III subunits (Polr1C, Polr1D) appear in each enzyme they belong
  to, following the FlyBase subgroups. Polr2M (Gdown1 homolog) is listed by
  FlyBase in RNA polymerase II but is an associated factor rather than one of
  the twelve core subunits. Mitochondrial RNA polymerase and the general
  transcription factors are outside the module.