mRNA capping enzyme complex

GO:0031533 · Other · Multiprotein complex · Proposed

A protein complex that consists of an RNA 5' triphosphatase and a guanyl transferase (Cet1p and Ceg1p in S. cerevisiae; Pct1 and Ceg1 in S. pombe) and is involved in mRNA capping. [GO:0031533]

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
Cet1 RNA 5'-triphosphatase subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	CET1		UNKNOWN	RNA 5'-triphosphatase constituent of the Saccharomyces cerevisiae mRNA capping enzyme complex. `GO:0031533` GO:0031533 defines the Saccharomyces mRNA capping enzyme complex as containing Cet1p RNA 5'-triphosphatase and Ceg1p guanyltransferase subunits.
Ceg1 guanyltransferase subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	CEG1		UNKNOWN	Guanyltransferase constituent of the Saccharomyces cerevisiae mRNA capping enzyme complex. `GO:0031533` GO:0031533 defines the Saccharomyces mRNA capping enzyme complex as containing Cet1p RNA 5'-triphosphatase and Ceg1p guanyltransferase subunits.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast has an mRNA capping enzyme complex containing Cet1p RNA 5'-triphosphatase and Ceg1p guanyltransferase subunits. [GO:0031533]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Reference budding-yeast system named in the GO:0031533 definition as containing Cet1p and Ceg1p. [GO:0031533]

Functions

7-methylguanosine mRNA capping GO:0006370 — The mRNA capping enzyme complex participates in mRNA capping.
- GO:0031533 GO:0031533 defines the mRNA capping enzyme complex as involved in mRNA capping.
- GO:0006370 GO:0006370 is the Gene Ontology biological-process term for 7-methylguanosine mRNA capping.

Mechanism graphs

mRNA capping enzyme complex caps nascent mRNA (FUNCTION)

Cet1p and Ceg1p form the Saccharomyces cerevisiae mRNA capping enzyme complex that participates in mRNA capping.

Subject	Predicate	Object	Evidence
Cet1 RNA 5'-triphosphatase subunit	contributes to	mRNA capping enzyme complex	`GO:0031533` GO:0031533 defines the Saccharomyces mRNA capping enzyme complex as containing Cet1p and Ceg1p.
Ceg1 guanyltransferase subunit	contributes to	mRNA capping enzyme complex	`GO:0031533` GO:0031533 defines the Saccharomyces mRNA capping enzyme complex as containing Cet1p and Ceg1p.
mRNA capping enzyme complex	supports	7-methylguanosine mRNA capping	`GO:0031533` GO:0031533 defines the mRNA capping enzyme complex as involved in mRNA capping. `GO:0006370` GO:0006370 is the biological-process term for 7-methylguanosine mRNA capping.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral family groundings for the Cet1 and Ceg1 constituents of the mRNA capping enzyme complex. GO:0031533 exactly identifies the mRNA capping enzyme complex and names the budding-yeast Cet1p and Ceg1p constituents, but exact source-neutral InterPro, Pfam, NCBIfam or UniProtKB family CURIEs for the RNA 5'-triphosphatase and guanyltransferase subunit classes were not curated in this pass.

Evidence

GO:0031533 Gene Ontology cellular-component term for the mRNA capping enzyme complex.
GO:0140513 Gene Ontology cellular-component parent term for nuclear protein-containing complexes.
GO:0006370 Gene Ontology biological-process term for 7-methylguanosine mRNA capping.
PMID:10347220 PubMed identifier for Saha et al. 1999, one of the GO:0031533 definition sources.
DOI:10.1074/jbc.274.23.16553 DOI for Saha et al. 1999, verified through PubMed.
PMID:12455993 PubMed identifier for Takagi et al. 2002, one of the GO:0031533 definition sources.
DOI:10.1128/EC.1.3.448-457.2002 DOI for Takagi et al. 2002, verified through PubMed and PMC.
PMID:9345280 PubMed identifier for Tsukamoto et al. 1997, one of the GO:0031533 definition sources.
DOI:10.1006/bbrc.1997.7439 DOI for Tsukamoto et al. 1997, verified through PubMed.

Curation history

2026-09-27T13:23:42Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-27T13:24:42Z codex · EXPANDED_RECORD — Added nuclear protein-containing-complex parentage, Cet1 and Ceg1 reviewed-label-only budding-yeast constituent rows, yeast scope, mRNA-capping function evidence, GO/PubMed/DOI evidence, a nonmechanistic function graph, and an mRNA-capping-enzyme subunit-grounding TODO.
2026-09-27T13:25:17Z codex · NORMALIZE_LOCAL_ID — Renamed the mRNA-capping function_id to lowercase snake case.

Source: data/structures/other/mrna_capping_enzyme_complex.yaml