module: dmel_histone_mrna_3prime_processing
title: Replication-dependent histone pre-mRNA 3' end processing in Drosophila melanogaster
label: Histone pre-mRNA 3' end processing
module_type: PROTEIN_COMPLEX
description: >-
  Replication-dependent histone mRNAs are not polyadenylated; instead their 3'
  end is formed by a single endonucleolytic cleavage between a conserved stem-loop
  and a purine-rich histone downstream element. The stem-loop binding protein
  (Slbp) binds the stem-loop, and the U7 snRNP, whose U7 snRNA base pairs with the
  downstream element and whose Sm ring contains the U7-specific Lsm10 and Lsm11,
  recruits FLASH and the histone pre-mRNA cleavage complex. This complex reuses
  the Cpsf73 endonuclease, Cpsf100 and Symplekin together with other CPSF and CstF
  subunits. In Drosophila these factors concentrate in the histone locus body.
summary: >-
  Slbp, the U7 snRNP, FLASH and the histone pre-mRNA cleavage complex, which cut
  histone pre-mRNAs after the stem-loop.
concepts:
  - {id: GO:0071204, label: histone pre-mRNA 3'end processing complex}
cellular_components:
  - {id: GO:0035363, label: histone locus body}
parts:
  - id: stem_loop_binding
    label: Stem-loop binding protein
    role: histone mRNA stem-loop recognition
    genes: [Slbp]
    complex: false
    function: {id: GO:0071207, label: histone pre-mRNA stem-loop binding}
    processes:
      - {id: GO:0006398, label: mRNA 3'-end processing by stem-loop binding and cleavage}
  - id: u7_snrnp
    label: U7 snRNP
    role: histone downstream element recognition
    group: U7
    complex_term: {id: GO:0005683, label: U7 snRNP}
    processes:
      - {id: GO:0006398, label: mRNA 3'-end processing by stem-loop binding and cleavage}
  - id: flash
    label: FLASH
    role: U7 snRNP-cleavage complex bridge
    genes: [FLASH]
    complex: false
  - id: histone_cleavage_complex
    label: Histone pre-mRNA cleavage complex
    role: histone pre-mRNA endonucleolytic cleavage
    group: HCC
    unit_functions:
      Cpsf73: {id: GO:0004521, label: RNA endonuclease activity}
    processes:
      - {id: GO:0006398, label: mRNA 3'-end processing by stem-loop binding and cleavage}
connections:
  - {source: u7_snrnp, target: histone_cleavage_complex, connection_type: POSITIVELY_REGULATES, description: The U7 snRNP with FLASH recruits the cleavage complex to the histone pre-mRNA.}
notes: >-
  Boundary. FlyBase's HPF group is the union of HCC, U7 and Slbp plus FLASH,
  and all members are covered by the four parts. The histone pre-mRNA cleavage
  complex shares all its subunits with the polyadenylation machinery in
  dmel_cleavage_polyadenylation. The core Sm proteins of the U7 snRNP (SmB,
  SmD3, SmE, SmF, SNRPG) are shared with spliceosomal snRNPs. snRNA:U7 has no
  protein product and is grounded to its FlyBase gene id.