nuclear exosome focus

GO:1990251 · Other · Other · Proposed

An nuclear body involved in nuclear mRNA surveilllance. Contains at least Mmi1, or an ortholog of it, and the nuclear exosome. [GO:1990251]

Synonyms: Mmi1 nuclear focus

Part of: nuclear lumen (GO:0031981)

Has part: nuclear exosome (RNase complex) (GO:0000176)

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
Mmi1	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	mmi1		UNKNOWN	YTH-family RNA-binding constituent that forms nuclear foci for selective elimination of meiosis-specific mRNAs. `PMID:16823445` Harigaya et al. 2006 found that fission-yeast Mmi1 forms multiple nuclear foci during vegetative growth. `DOI:10.1371/journal.pgen.1008598` Shichino et al. 2020 analyzed Mmi1 foci and the MTREC/NURS-dependent recruitment of the nuclear exosome to those foci.
nuclear exosome (RNase complex)	Protein complex	part of	`GO:0000176`			UNKNOWN	Nuclear RNase complex recruited to Mmi1 foci for exosome-mediated elimination of meiotic transcripts. `GO:1990251` GO:1990251 defines nuclear exosome foci as containing Mmi1 or an ortholog and the nuclear exosome. `DOI:10.1371/journal.pgen.1008598` Shichino et al. 2020 showed that the fission-yeast nuclear exosome colocalizes with Mmi1 foci and is recruited there through MTREC/NURS.

Taxonomic distribution

NCBITaxon:4896 Schizosaccharomyces pombe — VARIABLE: Mmi1 nuclear foci were observed in vegetatively growing fission-yeast cells, where MTREC/NURS links Mmi1 to the nuclear exosome for meiotic transcript elimination. [DOI:10.1371/journal.pgen.1008598]

Canonical examples

NCBITaxon:4896 Schizosaccharomyces pombe — Shichino et al. localized the nuclear exosome to Mmi1-positive nuclear foci in vegetatively growing Schizosaccharomyces pombe. [DOI:10.1371/journal.pgen.1008598]

Functions

nuclear mRNA surveillance of meiosis-specific transcripts GO:0033621 — Mmi1 nuclear exosome foci couple the YTH-family Mmi1 surveillance factor to nuclear-exosome decay of DSR-containing meiosis-specific transcripts during vegetative fission-yeast growth.
- GO:0033621 GO:0033621 is the biological-process term for YTH-family-protein-dependent nuclear mRNA surveillance of meiosis-specific transcripts.
- PMID:16823445 Harigaya et al. 2006 discovered the DSR-Mmi1 system for selective elimination of meiosis-specific transcripts in vegetative fission yeast.
- DOI:10.1371/journal.pgen.1008598 Shichino et al. 2020 connected Mmi1 foci, MTREC/NURS and nuclear-exosome recruitment in the same elimination pathway.

Mechanism graphs

MTREC/NURS recruits exosome to Mmi1 foci (FUNCTION)

Fission-yeast Mmi1 forms nuclear foci that recruit the nuclear exosome through MTREC/NURS to eliminate meiosis-specific mRNAs during vegetative growth.

Subject	Predicate	Object	Evidence
Mmi1	localizes to	nuclear exosome focus	`PMID:16823445` Harigaya et al. 2006 found Mmi1 in multiple nuclear foci during vegetative growth.
MTREC/NURS complex	recruits	nuclear exosome (RNase complex)	`DOI:10.1371/journal.pgen.1008598` Shichino et al. 2020 showed that MTREC/NURS connects Mmi1 and the nuclear exosome in fission yeast.
nuclear exosome (RNase complex)	localizes to	nuclear exosome focus	`GO:1990251` GO:1990251 defines nuclear exosome foci as containing the nuclear exosome. `DOI:10.1371/journal.pgen.1008598` Shichino et al. 2020 found nuclear exosome colocalization at Mmi1 foci.
nuclear exosome focus	supports	nuclear mRNA surveillance of meiosis-specific transcripts	`GO:1990251` GO:1990251 defines the focus as a nuclear body involved in nuclear mRNA surveillance. `GO:0033621` GO:0033621 is the exact GO process for YTH-family-protein-dependent degradation of meiosis-specific transcripts.

Discussions

CURATION_TODO (OPEN): Resolve whether MTREC/NURS, Red1, Mtl1 and meiosis-specific transcript substrates are stable constituents of the nuclear exosome focus. This first GO:1990251 record captures the GO-defined Mmi1 and nuclear-exosome focus. Shichino et al. 2020 establish that MTREC/NURS links Mmi1 to the nuclear exosome, but the exact focus residency of Red1, Mtl1 and Mmi1-bound meiotic RNA substrates should be curated before adding them as components.

Evidence

GO:1990251 Gene Ontology cellular-component term for nuclear exosome focus, with definition provenance from PMID:16823445, PMID:23980030 and PMID:32012158.
GO:0016604 Gene Ontology cellular-component parent term for nuclear body.
GO:0031981 Gene Ontology cellular-component term for the nuclear lumen; Mmi1/exosome foci are nuclear bodies.
GO:0000176 Gene Ontology cellular-component term for the nuclear exosome RNase complex, the exosome component in GO:1990251.
GO:0033621 Gene Ontology biological-process term for nuclear mRNA surveillance of meiosis-specific transcripts.
PMID:16823445 Harigaya, Tanaka, Yamanaka and colleagues 2006, Selective elimination of messenger RNA prevents an incidence of untimely meiosis, Nature.
DOI:10.1093/nar/gkt763 Yamashita, Takayama, Iwata and Yamamoto 2013, A novel factor Iss10 regulates Mmi1-mediated selective elimination of meiotic transcripts, Nucleic Acids Research.
DOI:10.1371/journal.pgen.1008598 Shichino, Otsubo, Yamamoto and Yamashita 2020, Meiotic gene silencing complex MTREC/NURS recruits the nuclear exosome to YTH-RNA-binding protein Mmi1, PLoS Genetics.

Curation history

2026-09-28T04:55:33Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-28T04:56:53Z codex · EXPANDED_RECORD — Added nuclear-exosome-focus GO synonymy, nuclear-body parentage, nuclear-lumen parthood, Mmi1 and nuclear-exosome components, Schizosaccharomyces pombe scope, meiotic-transcript-surveillance function evidence, a nonmechanistic MTREC/NURS recruitment graph and a component-boundary TODO.

Source: data/structures/other/nuclear_exosome_focus.yaml