mitochondrial nucleoid

GO:0042645 · Nucleoid · Subcellular region · Proposed

The region of a mitochondrion to which the DNA is confined. [GO:0042645]

Synonyms: mitochondrion nucleoid; mitochromosome

Part of: mitochondrial matrix (GO:0005759)

Xrefs: uniprot.location:SL-0269 — Mitochondrion nucleoid

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
mitochondrial DNA	Dna	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Mitochondrial genome DNA packaged with DNA-binding proteins into nucleoprotein foci inside the mitochondrial matrix. `DOI:10.1242/jcs.028605` Kucej et al. 2008 assayed Saccharomyces cerevisiae mitochondrial DNA organization in nucleoids under different metabolic states. `DOI:10.1016/j.tcb.2007.08.007` Kucej and Butow 2007 review mitochondrial nucleoids as nucleoprotein structures that package and maintain mitochondrial DNA.
mitochondrial HMG-box DNA-binding proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	High-mobility-group DNA-binding proteins represented by Saccharomyces cerevisiae Abf2 that bind and package mtDNA within mitochondrial nucleoids. `DOI:10.1242/jcs.028605` Kucej et al. 2008 used ChIP-on-chip to show that Saccharomyces cerevisiae Abf2 binds most of the mitochondrial genome in vivo. `DOI:10.1534/genetics.108.095786` Sia et al. 2009 studied loss of the abundant Saccharomyces cerevisiae mitochondrial nucleoid-associated protein Abf2p.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Mitochondrial nucleoids and their Abf2-containing mtDNA packaging machinery have been characterized in budding yeast. [DOI:10.1242/jcs.028605]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Yeast model in which Abf2 binds and packages mtDNA in mitochondrial nucleoids and nucleoid organization changes with metabolic state. [DOI:10.1242/jcs.028605]

Functions

mitochondrial genome maintenance — The mitochondrial nucleoid packages mitochondrial DNA into matrix-localized nucleoprotein foci that support mtDNA organization and stability.
- DOI:10.1242/jcs.028605 Kucej et al. 2008 connected Abf2-mediated mtDNA packaging and metabolic remodeling with yeast mitochondrial nucleoid organization.
- DOI:10.1534/genetics.108.095786 Sia et al. 2009 showed that loss of yeast Abf2p destabilizes repetitive mitochondrial DNA.

Mechanism graphs

Abf2 helps package yeast mtDNA into mitochondrial nucleoids (FUNCTION)

In Saccharomyces cerevisiae, the mitochondrial HMG-box protein Abf2 binds broadly across mtDNA and supports its packaging and stability in matrix-localized mitochondrial nucleoids.

Subject	Predicate	Object	Evidence
mitochondrial HMG-box DNA-binding proteins	bind	mitochondrial DNA	`DOI:10.1242/jcs.028605` Kucej et al. 2008 mapped Abf2 binding across Saccharomyces cerevisiae mtDNA by in organello ChIP-on-chip.
mitochondrial DNA	is packaged in	mitochondrial nucleoid	`DOI:10.1016/j.tcb.2007.08.007` Kucej and Butow 2007 review the architecture of protein-bound mitochondrial nucleoids.
mitochondrial HMG-box DNA-binding proteins	supports	mitochondrial genome maintenance	`DOI:10.1534/genetics.108.095786` Sia et al. 2009 measured increased mitochondrial frameshifts and direct-repeat deletions after loss of Abf2p.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings for mitochondrial DNA and mitochondrial nucleoid-associated protein classes before adding additional mtDNA packaging factors. This first mitochondrial nucleoid record keeps mtDNA and the Abf2-represented HMG-box protein component reviewed-label-only to avoid guessing Sequence Ontology or protein-family CURIEs.

Evidence

GO:0042645 Gene Ontology cellular-component term for mitochondrial nucleoid.
uniprot.location:SL-0269 — Mitochondrion nucleoid UniProt subcellular-location entry for mitochondrion nucleoid maps to GO:0042645.
DOI:10.1016/j.tcb.2007.08.007 Kucej and Butow 2007, Evolutionary tinkering with mitochondrial nucleoids, Trends in Cell Biology.
DOI:10.1242/jcs.028605 Kucej et al. 2008, Mitochondrial nucleoids undergo remodeling in response to metabolic cues, Journal of Cell Science.
DOI:10.1534/genetics.108.095786 Sia et al. 2009, Loss of the Mitochondrial Nucleoid Protein, Abf2p, Destabilizes Repetitive DNA in the Yeast Mitochondrial Genome, Genetics.

Curation history

2026-09-12T11:41:09Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-12T11:42:03Z codex · EXPANDED_RECORD — Added nucleoid parentage, mitochondrial-matrix parthood, the UniProt SL-0269 synonym and xref, reviewed-label-only mitochondrial DNA and HMG-box protein components, Saccharomyces cerevisiae scope, mitochondrial genome maintenance, a nonmechanistic Abf2 packaging graph, and a component-grounding TODO.
2026-09-12T11:44:50Z codex · REFINED_RECORD — Removed obsolete GO:0000002 groundings from the mitochondrial genome maintenance function and graph node after identifier-label validation flagged the term as obsolete.
2026-09-12T11:51:54Z codex · ADDRESS_REVIEW — Resolved #640 by adding the UniProt SL-0269 preferred label as an exact synonym, and resolved #641 by rewording the mtDNA-to-nucleoid packaging edge so mitochondrial DNA is not modeled as the active packaging agent.

Source: data/structures/nucleoid/mitochondrial_nucleoid.yaml