histone locus body

GO:0035363 · Ribonucleoprotein · Other · Proposed

A nuclear body associated with the histone gene locus that is thought to contain all of the factors necessary for histone mRNA transcription and pre-mRNA processing. In Drosophila, U7 snRNP is located in the histone locus body rather than the distinct Cajal body. [GO:0035363]

Synonyms: HLB

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
NPAT/Mxc scaffold protein	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	NPAT, mxc	ESSENTIAL	Scaffold protein concentrated at replication-dependent histone gene loci that promotes histone locus body assembly. `DOI:10.1091/mbc.E14-10-1445` Terzo et al. 2015 tested Multi Sex Combs accumulation and formation functions in the Drosophila histone locus body. `DOI:10.1074/jbc.M114.616466` Yang et al. 2014 analyzed a conserved NPAT/Mxc interaction that is essential for histone locus body biogenesis.
FLASH	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	FLASH	ESSENTIAL	HLB resident protein that interacts with NPAT/Mxc and supports histone locus body biogenesis. `DOI:10.1074/jbc.M114.616466` Yang et al. 2014 characterized the NPAT/Mxc-FLASH interaction in HLB biogenesis. `DOI:10.1091/mbc.E20-03-0176` Koreski et al. 2020 analyzed multiple Drosophila HLB assembly interactions involving Mxc and FLASH.
U7 snRNP	Protein complex	part of	`GO:0005683`		UNKNOWN	Ribonucleoprotein component of histone 3'-end processing that localizes to the HLB in Drosophila. `GO:0035363` GO:0035363 states that U7 snRNP is located in the Drosophila histone locus body rather than in a distinct Cajal body. `DOI:10.1083/jcb.200511038` Liu et al. 2006 localized Drosophila U7 snRNP to a separate histone locus body associated with the histone gene locus.

Taxonomic distribution

NCBITaxon:7227 Drosophila melanogaster — VARIABLE: Drosophila melanogaster was used to define the HLB as a U7 snRNP-containing nuclear body associated with the histone gene locus. [DOI:10.1083/jcb.200511038]
NCBITaxon:9606 Homo sapiens — VARIABLE: Human NPAT and FLASH were used to define a conserved interaction required for HLB biogenesis. [DOI:10.1074/jbc.M114.616466]

Canonical examples

NCBITaxon:7227 Drosophila melanogaster — Drosophila embryos and cultured cells were used to characterize developmental and cell-cycle regulation of HLBs associated with the replication-dependent histone gene locus. [DOI:10.1091/mbc.e06-11-1033]

Functions

replication-dependent histone mRNA biogenesis — Histone locus bodies concentrate replication-dependent histone transcription and pre-mRNA processing factors at the histone gene cluster.
- DOI:10.1080/15476286.2016.1265198 Duronio and Marzluff 2017 reviewed HLB assembly and function in cell-cycle-regulated histone gene expression.
- DOI:10.1083/jcb.201504043 Tatomer et al. 2016 showed that concentrating pre-mRNA processing factors in the HLB facilitates efficient Drosophila histone mRNA biogenesis.

Mechanism graphs

NPAT/Mxc and FLASH organize the HLB (ASSEMBLY)

Histone locus bodies are nuclear ribonucleoprotein granules organized at replication-dependent histone gene loci by the NPAT/Mxc scaffold, FLASH and U7 snRNP.

Subject	Predicate	Object	Evidence
NPAT/Mxc scaffold protein	scaffolds	histone locus body	`DOI:10.1091/mbc.E14-10-1445` Terzo et al. 2015 connected Drosophila Mxc domains with Mxc accumulation in and formation of HLBs.
NPAT/Mxc scaffold protein	interacts with	FLASH	`DOI:10.1074/jbc.M114.616466` Yang et al. 2014 analyzed the conserved NPAT/Mxc-FLASH interaction needed for HLB biogenesis. `DOI:10.1091/mbc.E20-03-0176` Koreski et al. 2020 extended Drosophila Mxc-FLASH assembly interaction analysis.
U7 snRNP	localizes to	histone locus body	`DOI:10.1083/jcb.200511038` Liu et al. 2006 localized U7 snRNP to the Drosophila HLB. `GO:0035363` GO:0035363 describes U7 snRNP localization to the Drosophila HLB.
histone locus body	concentrates	replication-dependent histone mRNA biogenesis	`DOI:10.1083/jcb.201504043` Tatomer et al. 2016 analyzed HLB concentration of pre-mRNA processing factors in Drosophila histone mRNA biogenesis. `DOI:10.1080/15476286.2016.1265198` Duronio and Marzluff 2017 reviewed HLB assembly and function in regulated histone gene expression.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral protein families and additional histone 3'-end-processing factors resident in the HLB. This first HLB record captures broad label-only NPAT/Mxc and FLASH scaffolding plus the GO-grounded U7 snRNP while leaving exact ortholog family grounding, HINFP, Symplekin, CPSF73, SLBP and other transcription and histone 3'-end-processing factor boundaries to a separate curation pass.

Evidence

GO:0035363 Gene Ontology cellular-component term for histone locus body and its exact HLB synonym.
GO:0140168 Gene Ontology cellular-component parent term for nuclear ribonucleoprotein granule.
GO:0031981 Gene Ontology cellular-component term for nuclear lumen.
GO:0005683 Gene Ontology cellular-component term for the U7 snRNP.
DOI:10.1083/jcb.200511038 Liu, Murphy, Buszczak and colleagues 2006, The Drosophila melanogaster Cajal body, Journal of Cell Biology.
DOI:10.1091/mbc.e06-11-1033 White, Leslie, Calvi, Marzluff and Duronio 2007, Developmental and Cell Cycle Regulation of the Drosophila Histone Locus Body, Molecular Biology of the Cell.
DOI:10.1101/cshperspect.a000653 Nizami, Deryusheva and Gall 2010, The Cajal Body and Histone Locus Body, Cold Spring Harbor Perspectives in Biology.
DOI:10.1091/mbc.E14-10-1445 Terzo et al. 2015, Distinct self-interaction domains promote Multi Sex Combs accumulation in and formation of the Drosophila histone locus body, Molecular Biology of the Cell.
DOI:10.1074/jbc.M114.616466 Yang, Sabath, Kunduru and colleagues 2014, A Conserved Interaction That Is Essential for the Biogenesis of Histone Locus Bodies, Journal of Biological Chemistry.
DOI:10.1083/jcb.201504043 Tatomer et al. 2016, Concentrating pre-mRNA processing factors in the histone locus body facilitates efficient histone mRNA biogenesis, Journal of Cell Biology.
DOI:10.1080/15476286.2016.1265198 Duronio and Marzluff 2017, Coordinating cell cycle-regulated histone gene expression through assembly and function of the Histone Locus Body, RNA Biology.
DOI:10.1091/mbc.E20-03-0176 Koreski, Rieder, McLain and colleagues 2020, Drosophila histone locus body assembly and function involves multiple interactions, Molecular Biology of the Cell.

Curation history

2026-09-28T00:41:14Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-28T00:42:12Z codex · EXPANDED_RECORD — Added GO HLB synonymy, nuclear-RNP-granule parentage, nuclear-lumen parthood, label-only NPAT/Mxc and FLASH components, a GO-grounded U7 snRNP component, Drosophila and human HLB taxonomic scope, a Drosophila canonical example, histone mRNA biogenesis function evidence, DOI/GO evidence, a nonmechanistic HLB organization graph and a component-boundary TODO.
2026-09-28T01:02:22Z codex · RESOLVED_REVIEW — Resolved #1693 by narrowing the Drosophila taxonomic-scope and canonical-example notes so Liu et al. 2006 and White et al. 2007 are not asked to support later Mxc/FLASH assembly claims.

Source: data/structures/ribonucleoprotein/histone_locus_body.yaml