Isw1b complex

GO:0036437 · Other · Multiprotein complex · Proposed

An Isw1 complex that binds DNA and has nucleosome-stimulated ATPase activity. In S. cerevisiae, contains an Isw1p ATPase subunit in complex with Ioc2p and Ioc4p. [GO:0036437]

Synonyms: ISW1b

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

Components

Component	Type	Part of / acts on	Grounding	Genes	Essential	Role
Isw1 Isw1b ATPase subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	ISW1	UNKNOWN	ISWI-family ATPase constituent of the budding-yeast Isw1b chromatin-remodeling complex. `DOI:10.1128/MCB.23.1.80-91.2003` Vary et al. 2003 separated the budding-yeast Isw1b complex from Isw1a and identified Isw1p as the shared ATPase subunit.
Ioc2 Isw1b subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	IOC2	UNKNOWN	Ioc protein constituent specific to the budding-yeast Isw1b complex. `DOI:10.1128/MCB.23.1.80-91.2003` Vary et al. 2003 found that Ioc2p and Ioc4p were mutually dependent for stable association with Isw1p and that Ioc2p copurified near-stoichiometric Isw1p and Ioc4p.
Ioc4 Isw1b subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	IOC4	UNKNOWN	Ioc protein constituent specific to the budding-yeast Isw1b complex. `DOI:10.1128/MCB.23.1.80-91.2003` Vary et al. 2003 found that Ioc2p and Ioc4p were mutually dependent for stable association with Isw1p and that Ioc2p copurified near-stoichiometric Isw1p and Ioc4p.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast is the source organism in which Vary et al. separated Isw1b from the related Isw1a complex. [DOI:10.1128/MCB.23.1.80-91.2003]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Vary et al. 2003 purified Isw1p- and Ioc2p-associated complexes from Saccharomyces cerevisiae and resolved the three-subunit Isw1b complex. [DOI:10.1128/MCB.23.1.80-91.2003]

Functions

chromatin remodeling GO:0006338 — The Isw1b complex is an ATP-dependent chromatin-remodeling complex with nucleosome-stimulated ATPase activity.
- GO:0006338 GO:0006338 is the Gene Ontology biological-process term for chromatin remodeling.
- GO:0036437 GO:0036437 defines Isw1b as an Isw1 chromatin complex with nucleosome-stimulated ATPase activity.

Mechanism graphs

Isw1b carries yeast chromatin remodeling (FUNCTION)

In Saccharomyces cerevisiae, Isw1, Ioc2, and Ioc4 form the Isw1b chromatin-remodeling complex.

Subject	Predicate	Object	Evidence
Isw1 Isw1b ATPase subunit	contributes to	Isw1b complex	`DOI:10.1128/MCB.23.1.80-91.2003` Vary et al. 2003 identified Isw1p in the budding-yeast Isw1b complex.
Ioc2 Isw1b subunit	contributes to	Isw1b complex	`DOI:10.1128/MCB.23.1.80-91.2003` Vary et al. 2003 identified Ioc2p in the budding-yeast Isw1b complex.
Ioc4 Isw1b subunit	contributes to	Isw1b complex	`DOI:10.1128/MCB.23.1.80-91.2003` Vary et al. 2003 identified Ioc4p in the budding-yeast Isw1b complex.
Isw1b complex	enables	chromatin remodeling	`GO:0036437` GO:0036437 defines the Isw1b cellular component as an Isw1 chromatin complex with nucleosome-stimulated ATPase activity.

Discussions

CURATION_TODO (OPEN): Curate exact source-neutral InterPro, Pfam, NCBIfam or UniProt family groundings for the Isw1b ATPase, Ioc2 and Ioc4 component classes when terms that denote those classes can be verified. The Isw1 ATPase is shared between Isw1a and Isw1b, and the available Ioc2 and Ioc4 motifs are broader than the Isw1b subunit classes, so exact grounding should avoid broad ATPase, PHD, or PWWP domain terms that do not denote these subunit classes.

Evidence

GO:0036437 Gene Ontology cellular-component term for the Isw1b complex.
GO:0016587 Gene Ontology cellular-component parent term for Isw1 complexes.
GO:0006338 Gene Ontology biological-process term for chromatin remodeling.
PMID:12482963 PubMed identifier for Vary et al. 2003, the Molecular and Cellular Biology paper that identified the separable budding-yeast Isw1a and Isw1b complexes.
DOI:10.1128/MCB.23.1.80-91.2003 DOI for Vary et al. 2003, 'Yeast Isw1p forms two separable complexes in vivo', verified through NCBI E-utilities.

Curation history

2026-09-27T02:17:38Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-27T02:18:44Z codex · EXPANDED_RECORD — Added ISW1b exact synonymy, Isw1-complex parentage, Isw1, Ioc2, and Ioc4 constituent rows, yeast scope, chromatin-remodeling function, GO/PubMed/DOI evidence, a nonmechanistic function graph, and a subunit-grounding TODO.

Source: data/structures/other/isw1b_complex.yaml