checkpoint clamp complex

GO:0030896 · Other · Multiprotein complex · Proposed

Conserved heterotrimeric complex of PCNA-like proteins that is loaded onto DNA at sites of DNA damage. [GO:0030896]

Synonyms: CCC; Rad9-Hus1-Rad1 (9-1-1) clamp complex

Components

Component	Type	Part of / acts on	Grounding	Genes	Essential	Role
Rad9 checkpoint clamp subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	rad9	UNKNOWN	PCNA-like constituent of the fission-yeast Rad9-Rad1-Hus1 DNA damage checkpoint clamp. `GO:0030896` GO:0030896 lists Rad9 among the Schizosaccharomyces pombe checkpoint clamp subunit names. `DOI:10.1091/mbc.12.12.3744` Kaur et al. 2001 performed structure-function analysis of the fission-yeast Hus1-Rad1-Rad9 checkpoint complex.
Rad1 checkpoint clamp subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	rad1	UNKNOWN	PCNA-like constituent of the fission-yeast Rad9-Rad1-Hus1 DNA damage checkpoint clamp. `GO:0030896` GO:0030896 lists Rad1 among the Schizosaccharomyces pombe checkpoint clamp subunit names. `DOI:10.1091/mbc.12.12.3744` Kaur et al. 2001 performed structure-function analysis of the fission-yeast Hus1-Rad1-Rad9 checkpoint complex.
Hus1 checkpoint clamp subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	hus1	UNKNOWN	PCNA-like constituent of the fission-yeast Rad9-Rad1-Hus1 DNA damage checkpoint clamp. `GO:0030896` GO:0030896 lists Hus1 among the Schizosaccharomyces pombe checkpoint clamp subunit names. `DOI:10.1091/mbc.12.12.3744` Kaur et al. 2001 performed structure-function analysis of the fission-yeast Hus1-Rad1-Rad9 checkpoint complex.

NCBITaxon:4896 Schizosaccharomyces pombe — COMMON: Fission yeast has a Hus1-Rad1-Rad9 checkpoint clamp complex matching the Schizosaccharomyces pombe subunit names noted by GO:0030896. [DOI:10.1091/mbc.12.12.3744]

NCBITaxon:4896 Schizosaccharomyces pombe — Reference fission-yeast system in which Kaur et al. performed structure-function analysis of the Hus1-Rad1-Rad9 checkpoint complex. [DOI:10.1091/mbc.12.12.3744]

DNA damage response GO:0006974 — The checkpoint clamp complex is loaded onto damaged DNA and supports the cellular response to DNA damage.
- GO:0030896 GO:0030896 defines the checkpoint clamp complex as loaded onto DNA at sites of DNA damage.
- GO:0006974 GO:0006974 is the Gene Ontology biological-process term for DNA damage response.

The Rad9, Rad1 and Hus1 proteins form a checkpoint clamp that is loaded at damaged DNA and supports the DNA damage response.

Subject	Predicate	Object	Evidence
Rad9 checkpoint clamp subunit	contributes to	checkpoint clamp complex	`GO:0030896` GO:0030896 lists S. pombe Rad9 as a checkpoint clamp subunit. `DOI:10.1091/mbc.12.12.3744` Kaur et al. 2001 analyzed the fission-yeast Hus1-Rad1-Rad9 checkpoint complex.
Rad1 checkpoint clamp subunit	contributes to	checkpoint clamp complex	`GO:0030896` GO:0030896 lists S. pombe Rad1 as a checkpoint clamp subunit. `DOI:10.1091/mbc.12.12.3744` Kaur et al. 2001 analyzed the fission-yeast Hus1-Rad1-Rad9 checkpoint complex.
Hus1 checkpoint clamp subunit	contributes to	checkpoint clamp complex	`GO:0030896` GO:0030896 lists S. pombe Hus1 as a checkpoint clamp subunit. `DOI:10.1091/mbc.12.12.3744` Kaur et al. 2001 analyzed the fission-yeast Hus1-Rad1-Rad9 checkpoint complex.
checkpoint clamp complex	loads onto	damaged DNA	`GO:0030896` GO:0030896 defines the checkpoint clamp complex as loaded onto DNA at sites of DNA damage. `DOI:10.1016/j.dnarep.2004.03.032` Parrilla-Castellar et al. 2004 reviewed the Rad9-Hus1-Rad1 9-1-1 clamp complex.
checkpoint clamp complex	supports	DNA damage response	`GO:0030896` GO:0030896 defines the checkpoint clamp complex as being loaded at DNA damage sites. `GO:0006974` GO:0006974 is the biological-process term for DNA damage response.

CURATION_TODO (OPEN): Resolve exact source-neutral family groundings for the Rad9, Rad1 and Hus1 constituents of the checkpoint clamp complex. GO:0030896 exactly identifies the conserved Rad9-Rad1-Hus1 clamp, but exact InterPro, Pfam, NCBIfam or UniProtKB family boundaries for the three fission-yeast-modeled subunit classes need narrower follow-up curation.

GO:0030896 Gene Ontology cellular-component term for the checkpoint clamp complex.
GO:0140513 Gene Ontology cellular-component parent term for nuclear protein-containing complexes.
GO:0006974 Gene Ontology biological-process term for DNA damage response.
PMID:12531008 PubMed identifier for Carr 2002, the DNA Repair review cited by the GO:0030896 definition.
DOI:10.1016/s1568-7864(02)00165-9 DOI for Carr 2002, verified through PubMed.
PMID:11739777 PubMed identifier for Kaur et al. 2001, the Molecular Biology of the Cell paper on the fission-yeast Hus1-Rad1-Rad9 checkpoint complex.
DOI:10.1091/mbc.12.12.3744 DOI for Kaur et al. 2001, verified through PubMed and PMC.
PMID:15279787 PubMed identifier for Parrilla-Castellar et al. 2004, the DNA Repair review on the Rad9-Hus1-Rad1 9-1-1 clamp complex.
DOI:10.1016/j.dnarep.2004.03.032 DOI for Parrilla-Castellar et al. 2004, verified through PubMed.
PMID:19446481 PubMed identifier for Dore et al. 2009, the Molecular Cell paper on the Rad9-Rad1-Hus1 DNA damage checkpoint complex crystal structure.
DOI:10.1016/j.molcel.2009.04.027 DOI for Dore et al. 2009, verified through PubMed.

2026-09-27T11:45:03Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-27T11:46:17Z codex · EXPANDED_RECORD — Added GO checkpoint-clamp synonyms, nuclear protein-containing-complex parentage, three reviewed-label-only fission-yeast constituent rows, Schizosaccharomyces pombe scope, DNA-damage-response function evidence, GO/PubMed/DOI evidence, a nonmechanistic function graph, and a checkpoint-clamp subunit-grounding TODO.