nuclear speck

GO:0016607 · Ribonucleoprotein · Other · Proposed

A discrete extra-nucleolar subnuclear domain, 20-50 in number, in which splicing factors are seen to be localized by immunofluorescence microscopy. [GO:0016607]

Synonyms: nuclear speckle; nuclear speckles; splicing speckle; speckle domain; speckle focus

Part of: nuclear lumen (GO:0031981)

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
pre-mRNA splicing factor cohort	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	SRSF1, SRSF2	UNKNOWN	Pre-mRNA splicing factors concentrated in nuclear speckles and dynamically supplied to active transcription sites. `GO:0016607` GO:0016607 defines nuclear specks by localization of splicing factors in the domain. `DOI:10.1038/387523a0` Misteli, Caceres and Spector 1997 tracked a GFP-tagged pre-mRNA splicing factor between nuclear speckles and sites of transcription.
SON/SRRM2 scaffold proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	SON, SRRM2	ESSENTIAL	Large intrinsically disordered scaffold proteins that form the core structural framework of nuclear speckles. `DOI:10.7554/eLife.60579` Ilik et al. 2020 identified SON and SRRM2 as essential for nuclear speckle formation. `DOI:10.1242/jcs.206854` Fei et al. 2017 resolved SON in the central region of human nuclear speckles by super-resolution microscopy.
MALAT1 lncRNA	Rna	part of	Reviewed label only (reviewed name; no accession asserted)	MALAT1	UNKNOWN	Long noncoding RNA enriched in nuclear speckles and associated with SR-splicing-factor organization. `DOI:10.1016/j.molcel.2010.08.011` Tripathi et al. 2010 localized MALAT1 to nuclear speckles and connected it to SR-splicing-factor organization. `DOI:10.1242/jcs.206854` Fei et al. 2017 found MALAT1 enriched toward the periphery of human nuclear speckles.

Taxonomic distribution

NCBITaxon:9606 Homo sapiens — VARIABLE: Human cells were used to resolve SON, splicing-factor, MALAT1 and snRNA layering within nuclear speckles by super-resolution microscopy. [DOI:10.1242/jcs.206854]

Canonical examples

NCBITaxon:9606 Homo sapiens — Human cultured cells were used to resolve SON, splicing-factor, MALAT1 and snRNA layering within nuclear speckles. [DOI:10.1242/jcs.206854]

Functions

pre-mRNA splicing factor organization — Nuclear speckles concentrate pre-mRNA splicing factors and dynamically supply them to active transcription sites.
- DOI:10.1038/387523a0 Misteli, Caceres and Spector 1997 showed dynamic exchange of an SR splicing factor between nuclear speckles and transcription sites in living cells.
- DOI:10.1101/cshperspect.a000646 Spector and Lamond 2011 reviewed nuclear speckles as subnuclear domains enriched in pre-mRNA splicing factors.

Mechanism graphs

SON, SRRM2 and MALAT1 organize nuclear speckles (ASSEMBLY)

Human nuclear speckles concentrate pre-mRNA splicing factors on a SON/SRRM2 protein framework with MALAT1 lncRNA and small RNAs layered around protein-rich regions.

Subject	Predicate	Object	Evidence
SON/SRRM2 scaffold proteins	scaffolds	nuclear speck	`DOI:10.7554/eLife.60579` Ilik et al. 2020 identified SON and SRRM2 as essential nuclear-speckle scaffold proteins.
pre-mRNA splicing factor cohort	localizes to	nuclear speck	`GO:0016607` GO:0016607 defines nuclear specks as domains in which splicing factors are localized.
MALAT1 lncRNA	localizes to	nuclear speck	`DOI:10.1016/j.molcel.2010.08.011` Tripathi et al. 2010 localized MALAT1 RNA to nuclear speckles.
nuclear speck	organizes	pre-mRNA splicing factor organization	`DOI:10.1038/387523a0` Misteli, Caceres and Spector 1997 showed dynamic exchange of a pre-mRNA splicing factor between speckles and transcription sites. `DOI:10.1101/cshperspect.a000646` Spector and Lamond 2011 reviewed nuclear speckles as enriched splicing-factor compartments.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral RNA, SR-protein, snRNP and scaffold boundaries for nuclear-speckle resident components. This first nuclear-speck record captures broad label-only SR splicing-factor, SON/SRRM2 and MALAT1 constituents while leaving exact SR protein families, spliceosomal snRNP subtypes, SON/SRRM2 grounding, additional resident factors and MALAT1 transcript boundaries to a separate curation pass.

Evidence

GO:0016607 Gene Ontology cellular-component term for nuclear speck.
GO:0140168 Gene Ontology cellular-component ancestor term for nuclear ribonucleoprotein granule.
GO:0016604 Gene Ontology cellular-component ancestor term for nuclear body.
GO:0031981 Gene Ontology cellular-component ancestor term for nuclear lumen.
DOI:10.1093/nar/gkx759 Galganski, Urbanek and Krzyzosiak 2017, Nuclear speckles: molecular organization, biological function and role in disease, Nucleic Acids Research.
DOI:10.1101/cshperspect.a000646 Spector and Lamond 2011, Nuclear Speckles, Cold Spring Harbor Perspectives in Biology.
DOI:10.1038/387523a0 Misteli, Caceres and Spector 1997, The dynamics of a pre-mRNA splicing factor in living cells, Nature.
DOI:10.1242/jcs.206854 Fei et al. 2017, Quantitative analysis of multilayer organization of proteins and RNA in nuclear speckles at super resolution, Journal of Cell Science.
DOI:10.7554/eLife.60579 Ilik et al. 2020, SON and SRRM2 are essential for nuclear speckle formation, eLife.
DOI:10.1016/j.molcel.2010.08.011 Tripathi et al. 2010, The Nuclear-Retained Noncoding RNA MALAT1 Regulates Alternative Splicing by Modulating SR Splicing Factor Phosphorylation, Molecular Cell.

Curation history

2026-09-27T23:58:22Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-28T00:00:24Z codex · EXPANDED_RECORD — Added GO nuclear-speck synonymy, nuclear-RNP-granule and nuclear-body parentage, nuclear-lumen parthood, label-only pre-mRNA-splicing-factor, SON/SRRM2 and MALAT1 components, Homo sapiens scope, speckle splicing-factor organization evidence, DOI/GO evidence, a nonmechanistic nuclear-speck organization graph and a component-boundary TODO.
2026-09-28T00:01:01Z codex · TIGHTENED_EVIDENCE — Narrowed the Homo sapiens distribution row to the Fei et al. 2017 human nuclear-speckle organization claim that its reference directly supports.

Source: data/structures/ribonucleoprotein/nuclear_speck.yaml