Cajal body

GO:0015030 · Ribonucleoprotein · Other · Proposed

A class of nuclear body, first seen after silver staining by Ramon y Cajal in 1903, enriched in small nuclear ribonucleoproteins, and certain general RNA polymerase II transcription factors; ultrastructurally, they appear as a tangle of coiled, electron-dense threads roughly 0.5 micrometers in diameter; involved in aspects of snRNP biogenesis; the protein coilin serves as a marker for Cajal bodies. Some argue that Cajal bodies are the sites for preassembly of transcriptosomes, unitary particles involved in transcription and processing of RNA. [GO:0015030]

Synonyms: coiled body; Gemini of coiled bodies; Gems

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
coilin	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	COIL	UNKNOWN	Cajal-body marker protein concentrated in the nuclear focus and used as a scaffold-like resident in this first component model. `GO:0015030` GO:0015030 names coilin as a marker protein for Cajal bodies in the Cajal body definition. `PMID:10944589` Bellini 2000 reviewed coilin as more than a molecular marker of the Cajal/coiled body.
spliceosomal snRNP complex	Protein complex	part of	`GO:0097525`		UNKNOWN	Small nuclear ribonucleoprotein complexes that are enriched in Cajal bodies during snRNP maturation. `GO:0015030` GO:0015030 defines Cajal bodies as enriched in small nuclear ribonucleoproteins. `DOI:10.1080/15476286.2016.1231359` Machyna, Heyn and Neugebauer 2017 reviewed how Cajal bodies participate in snRNP biogenesis.
scaRNA	Rna	part of	`SO:0002095`		UNKNOWN	scaRNA guides that reside in Cajal bodies and modify spliceosomal snRNAs. `DOI:10.1093/emboj/21.11.2746` Darzacq et al. 2002 defined small Cajal body-specific RNAs as guides for post-transcriptional modification of spliceosomal snRNAs localized in Cajal bodies.

Taxonomic distribution

NCBITaxon:2759 Eukaryota — VARIABLE: Cajal bodies are nuclear ribonucleoprotein granules of eukaryotic cells, with visible bodies varying across lineage and cell state. [DOI:10.1146/annurev.cellbio.16.1.273]

Canonical examples

NCBITaxon:9606 Homo sapiens — Human cells were used to localize scaRNAs to Cajal bodies and connect them to spliceosomal snRNA modification. [DOI:10.1093/emboj/21.11.2746]

Functions

snRNP biogenesis — Cajal bodies concentrate snRNPs, coilin and scaRNAs in a nuclear body associated with maturation and modification of small nuclear ribonucleoprotein particles.
- DOI:10.1080/15476286.2016.1231359 Machyna, Heyn and Neugebauer 2017 reviewed Cajal bodies in relation to snRNP biogenesis.
- DOI:10.1093/emboj/21.11.2746 Darzacq et al. 2002 connected Cajal-body scaRNAs to guide-directed modification of spliceosomal snRNAs.

Mechanism graphs

Cajal-body residents support snRNP maturation (FUNCTION)

Cajal bodies are nuclear ribonucleoprotein granules that concentrate coilin, spliceosomal snRNP complexes and scaRNAs during small nuclear RNP biogenesis.

Subject	Predicate	Object	Evidence
coilin	marks	Cajal body	`GO:0015030` GO:0015030 names coilin as a Cajal-body marker. `PMID:10944589` Bellini 2000 reviewed coilin's relation to the Cajal/coiled body.
spliceosomal snRNP complex	are enriched in	Cajal body	`GO:0015030` GO:0015030 defines Cajal bodies as enriched in small nuclear ribonucleoproteins.
scaRNA	localize to	Cajal body	`DOI:10.1093/emboj/21.11.2746` Darzacq et al. 2002 localized scaRNA guide RNAs to Cajal bodies.
scaRNA	guide RNA modification during	snRNP biogenesis	`DOI:10.1093/emboj/21.11.2746` Darzacq et al. 2002 connected Cajal-body scaRNAs to guide RNA roles in spliceosomal snRNA methylation and pseudouridylation.
Cajal body	is associated with	snRNP biogenesis	`DOI:10.1080/15476286.2016.1231359` Machyna, Heyn and Neugebauer 2017 reviewed Cajal bodies and snRNP biogenesis.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral protein-family, scaRNP and telomerase-related boundaries for Cajal-body resident components. This first Cajal body record captures coilin, GO-grounded spliceosomal snRNP complexes and scaRNA guides as broad resident cohorts while leaving exact coilin family, scaRNP-protein, SMN/gemin and telomerase trafficking boundaries to a separate grounding pass.

Evidence

GO:0015030 Gene Ontology cellular-component term for Cajal body and its Cajal body synonymy.
GO:0140168 Gene Ontology cellular-component parent term for nuclear ribonucleoprotein granule.
GO:0031981 Gene Ontology cellular-component term for nuclear lumen.
GO:0097525 Gene Ontology cellular-component term for spliceosomal snRNP complex.
SO:0002095 Sequence Ontology term for small Cajal body-specific RNA.
DOI:10.1146/annurev.cellbio.16.1.273 Gall 2000 reviewed Cajal bodies and their coiled-body naming history.
PMID:10944589 PubMed identifier for Bellini 2000, Coilin, more than a molecular marker of the cajal (coiled) body.
DOI:10.1093/emboj/21.11.2746 Darzacq, Jady, Verheggen and colleagues 2002, Cajal body-specific small nuclear RNAs: a novel class of 2'-O-methylation and pseudouridylation guide RNAs, EMBO Journal.
DOI:10.1080/15476286.2016.1231359 Machyna, Heyn and Neugebauer 2017, Cajal bodies and snRNPs - friends with benefits, RNA Biology.

Curation history

2026-09-27T21:41:28Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-27T21:42:50Z codex · EXPANDED_RECORD — Added GO Cajal-body synonymy, nuclear RNP granule parentage, nuclear-lumen parthood, coilin, spliceosomal snRNP and scaRNA component curation, Eukaryota distribution, a human example, snRNP-biogenesis function evidence, GO/DOI/PMID evidence, a nonmechanistic Cajal-body RNP graph and a component-grounding TODO.
2026-09-27T21:48:20Z codex · FIXED_PRODUCT_LABELS — Aligned the GO:0097525 and SO:0002095 component and graph node labels with their canonical spliceosomal snRNP complex and scaRNA labels.
2026-09-27T22:02:25Z codex · RESOLVED_REVIEW — Resolved #1682 by narrowing the scaRNA graph edge so Cajal-body scaRNAs guide spliceosomal snRNA modification during snRNP maturation rather than catalytically modifying RNAs themselves.

Source: data/structures/ribonucleoprotein/cajal_body.yaml