module: dmel_9_1_1_checkpoint_clamp
title: Rad9-Hus1-Rad1 (9-1-1) checkpoint clamp in Drosophila melanogaster
label: 9-1-1 checkpoint clamp
module_type: PROTEIN_COMPLEX
description: >-
  The 9-1-1 complex is a heterotrimeric ring of Rad9, Hus1 and Rad1 that is
  structurally related to the PCNA sliding clamp. An RFC-like clamp loader
  places it at 5' recessed junctions of single-stranded DNA gaps and resected
  ends, where it helps recruit and activate the ATR kinase in the DNA damage
  and replication checkpoint. In Drosophila, the Hus1 ortholog is named
  Hus1-like.
summary: >-
  Heterotrimeric PCNA-like clamp loaded at damaged DNA that supports ATR
  checkpoint signalling.
concepts:
  - {id: GO:0030896, label: checkpoint clamp complex}
cellular_components:
  - {id: GO:0005634, label: nucleus}
group: CCC-911
roles:
  Rad9: Rad9 subunit of the clamp ring
  Hus1-like: Hus1 subunit of the clamp ring
  Rad1: Rad1 subunit of the clamp ring
notes: >-
  The clamp loader (Rad17-RFC in other species) is outside the module. Each
  subunit is modelled as a part because the trimer has no further
  sub-structure.
function_note: >-
  No molecular function is assigned. The 9-1-1 trimer is a DNA clamp that is
  loaded at damage sites and scaffolds checkpoint signalling; the GO term for
  DNA clamp activity (GO:0061777) is obsolete, and the 3'-5' exonuclease
  activity inferred for Rad9 (ISS) is not established for the fly protein.