cellular bud neck contractile ring

GO:0000142 · Cytoskeleton · Filament · Proposed

A contractile ring, i.e. a cytoskeletal structure composed of actin filaments and myosin, that forms beneath the plasma membrane at the mother-bud neck in mitotic cells that divide by budding in preparation for completing cytokinesis. An example of this structure is found in Saccharomyces cerevisiae. [GO:0000142]

Synonyms: neck ring

Part of: cellular bud neck (GO:0005935)

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
actin filaments	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	ACT1		UNKNOWN	Filamentous actin constituent of the contractile ring that forms beneath the mother-bud-neck plasma membrane. `GO:0000142` GO:0000142 defines the cellular bud neck contractile ring as a cytoskeletal structure composed of actin filaments and myosin. `DOI:10.1083/jcb.142.5.1301` Bi et al. 1998 characterized the Saccharomyces actin ring at the mother-bud neck during cytokinesis.
Myo1-family myosin-II motor	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	MYO1		UNKNOWN	Myosin-II constituent that localizes to the neck ring and participates in budding-yeast cytokinesis. `GO:0000142` GO:0000142 defines the cellular bud neck contractile ring as a cytoskeletal structure composed of actin filaments and myosin. `DOI:10.1083/jcb.142.5.1301` Bi et al. 1998 used Saccharomyces Myo1 localization at the mother-bud neck to study the cytokinetic actomyosin ring.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast forms a Myo1- and actin-containing contractile ring at the mother-bud neck during cytokinesis. [DOI:10.1083/jcb.142.5.1301]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model in which Myo1 and actin rings were tracked at the mother-bud neck during cytokinesis. [DOI:10.1083/jcb.142.5.1301]

Functions

bud-neck actomyosin cytokinesis — The cellular bud neck contractile ring forms beneath the mother-bud-neck plasma membrane in preparation for completing budding-yeast cytokinesis.
- GO:0000142 GO:0000142 defines the ring by its mother-bud-neck position and cytokinesis timing.
- DOI:10.1083/jcb.142.5.1301 Bi et al. 1998 directly tested Saccharomyces actomyosin-ring involvement in cytokinesis.

Mechanism graphs

Bud-neck actomyosin ring topology (ASSEMBLY)

Actin filaments and Myo1 form a contractile ring beneath the plasma membrane at the Saccharomyces mother-bud neck.

Subject	Predicate	Object	Evidence
actin filaments	contributes to	cellular bud neck contractile ring	`GO:0000142` GO:0000142 defines the ring as composed of actin filaments and myosin.
Myo1-family myosin-II motor	contributes to	cellular bud neck contractile ring	`DOI:10.1083/jcb.142.5.1301` Bi et al. 1998 followed Myo1 at the Saccharomyces neck ring during cytokinesis.
cellular bud neck contractile ring	is part of	cellular bud neck	`GO:0000142` GO:0000142 places the ring at the mother-bud neck of mitotic budding cells. `GO:0005935` GO:0005935 identifies the mother-daughter bud-neck region.

Discussions

INTERPRETATION (RESOLVED): Keep the cellular bud neck contractile ring distinct from the broader actomyosin ring and from bud-neck septin structures. GO:0000142 denotes the budding-cell mitotic actomyosin ring at the mother-bud neck. GO:0110085 denotes the broader mitotic actomyosin contractile ring class, GO:0005935 denotes the bud-neck region, and GO:0000144/GO:0032174 denote separate septin-rich bud-neck structures.
CURATION_TODO (OPEN): Resolve exact source-neutral family groundings and accessory boundaries for bud-neck contractile-ring proteins. This first localized bud-neck actomyosin-ring record keeps actin and myosin II reviewed-label only and avoids adding Iqg1/Cyk1, Hof1/Cyk2, Mlc1, or other cytokinetic factors until their constituent versus associated-machinery status has been reviewed explicitly.

Evidence

GO:0000142 Gene Ontology cellular-component term for the cellular bud neck contractile ring.
GO:0110085 Gene Ontology cellular-component parent for mitotic actomyosin contractile rings.
GO:0005935 Gene Ontology cellular-component term for the cellular bud neck containing the contractile ring.
DOI:10.1083/jcb.142.5.1301 Bi et al. 1998, 'Involvement of an actomyosin contractile ring in Saccharomyces cerevisiae cytokinesis', Journal of Cell Biology.
DOI:10.1016/j.tcb.2005.06.007 Versele and Thorner 2005, 'Some assembly required: yeast septins provide the instruction manual', Trends in Cell Biology.

Curation history

2026-09-29T21:26:18Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-29T21:27:39Z codex · EXPANDED_RECORD — Added GO synonymy, mitotic actomyosin-ring parentage, bud-neck parthood, reviewed-label-only actin and Myo1 constituents, Saccharomyces distribution and canonical example evidence, a bud-neck cytokinesis function, GO/DOI evidence, a nonmechanistic actomyosin-ring topology graph, and boundary and component-grounding discussions.

Source: data/structures/cytoskeleton/cellular_bud_neck_contractile_ring.yaml