SMC3 - Structural Maintenance of Chromosomes 3
<div class="infobox infobox-gene">
<h3>SMC3</h3>
<table>
<tr><th>Full Name</th><td>Structural Maintenance of Chromosomes 3</td></tr>
<tr><th>Symbol</th><td>SMC3</td></tr>
<tr><th>Chromosomal Location</th><td>10q25.2</td></tr>
<tr><th>NCBI Gene ID</th><td>[9126](https://www.ncbi.nlm.nih.gov/gene/9126)</td></tr>
<tr><th>OMIM</th><td>[606062](https://omim.org/entry/606062)</td></tr>
<tr><th>Ensembl ID</th><td>[ENSG00000103052](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000103052)</td></tr>
<tr><th>UniProt</th><td>[Q9UQE7](https://www.uniprot.org/uniprot/Q9UQE7)</td></tr>
<tr><th>Associated Diseases</th><td>Cornelia de Lange Syndrome, Cohesinopathy, [Cancer](/cancer)</td></tr>
</table>
</div>
Overview
Mermaid diagram (expand to render)
SMC3 (Structural Maintenance of Chromosomes 3) is a core subunit of the cohesin complex, a multi-protein ring structure essential for sister chromatid cohesion, DNA repair, and three-dimensional genome organization. Cohesin, composed of SMC1A, SMC3, RAD21, and SA1/SA2, topologically embraces DNA to regulate chromosome dynamics throughout the cell cycle["@nasmyth2009"]. In post-mitotic [neurons](/entities/neurons), cohesin plays critical roles in gene regulation, DNA damage response, and maintenance of genomic stability.
Function
Cohesin Complex Architecture
SMC3 forms one arm of the cohesin ring, dimerizing with [SMC1A](/genes/smc1a) through their hinge domains to create a V-shaped structure that, together with RAD21 bridging the ATPase head domains, encircles chromosomal DNA[@higashi2020]. The SMC3 ATPase head domain hydrolyzes ATP to drive conformational changes that regulate cohesin loading, translocation, and release from chromatin.
Sister Chromatid Cohesion
During S phase, the cohesin complex establishes cohesion between newly replicated sister chromatids, maintaining their association until anaphase onset. This cohesion is essential for accurate chromosome segregation and prevention of aneuploidy[@michaelis1997]. ESCO1 and ESCO2 acetyltransferases modify SMC3 to stabilize cohesive interactions.
Gene Regulation and Chromatin Architecture
In neurons and other post-mitotic cells, cohesin participates in:
- Loop extrusion: Generating topologically associating domains (TADs) that organize the genome into functional compartments
- Enhancer-promoter contacts: Facilitating long-range regulatory interactions
- Gene expression programs: Regulating activity-dependent neuronal gene expression[@rao2014]
DNA Damage Response
Cohesin is recruited to DNA double-strand breaks where it promotes:
- Homologous recombination repair
- Chromatin structure restoration
- Checkpoint signaling coordination[@watrin2006]
Disease Associations
Cornelia de Lange Syndrome (CdLS)
Heterozygous SMC3 mutations cause approximately 1-2% of CdLS cases, a multisystem developmental disorder characterized by:
- Distinctive facial dysmorphism
- Growth retardation
- Intellectual disability
- Limb abnormalities
- Gastroesophageal reflux[@deardorff2007]
SMC3-related CdLS typically presents with milder features compared to NIPBL mutations but with similar mechanistic basis involving disrupted cohesin function.
Neurodevelopmental Disorders
SMC3 variants are associated with:
- Intellectual disability: Disrupted cohesin-mediated gene regulation
- Autism spectrum disorder: Altered synaptic gene expression programs
- Seizures: Aberrant neuronal network development[@gomperts2009]
Cancer
Cohesin mutations, including SMC3 alterations, occur in various cancers:
- Glioblastoma
- Acute myeloid leukemia
- Ewing sarcoma
Dysregulated cohesin function may contribute to oncogenic transcriptional programs and genomic instability[@kon2013].
Expression
SMC3 is ubiquitously expressed across tissues, with particularly high expression in:
- Neural stem cells and progenitors
- Developing brain structures
- Actively dividing cell populations
In mature neurons, SMC3 expression persists, reflecting ongoing roles in chromatin organization and gene regulation rather than cell division[@wendt2008].
Allen Brain Atlas Data
SMC3 shows moderate, widespread expression throughout the adult human brain, with slightly elevated levels in:
- Cerebral [cortex](/brain-regions/cortex)
- [Hippocampus](/brain-regions/hippocampus)
- [Cerebellum](/brain-regions/cerebellum)
Therapeutic Implications
Targeting Cohesin Dysfunction
Therapeutic strategies for cohesinopathies focus on:
- [HDAC](/entities/hdac-enzymes) inhibitors: Vorinostat and related compounds that may partially rescue gene expression defects
- [mTOR](/mechanisms/mtor-signaling-pathway) modulation: Rapamycin derivatives affecting protein homeostasis
- Gene therapy: Future approaches for correcting specific mutations[@kline2018]
Cancer Applications
SMC3 and cohesin represent potential therapeutic targets in malignancies:
- Synthetic lethality approaches
- Combination with DNA damage response inhibitors
See Also
- [SMC1A](/genes/smc1a) - Cohesin complex partner
- [RAD21](/genes/rad21) - Cohesin ring component
- [NIPBL](/genes/nipbl) - Cohesin loader
- [ESCO1](/genes/esco1) - Cohesin acetyltransferase
- [ESCO2](/genes/esco2) - Cohesin acetyltransferase
- Cohesin Complex - Mechanism page
- [Cornelia de Lange Syndrome - Disease page](/proteins/ANG)
External Links
- [GeneCards: SMC3](https://www.genecards.org/cgi-bin/carddisp.pl?gene=SMC3)
- [UniProt: Q9UQE7](https://www.uniprot.org/uniprot/Q9UQE7)
- [Human Protein Atlas: SMC3](https://www.proteinatlas.org/ENSG00000103052-SMC3)
References
[Nasmyth K, Haering CH, Cohesin: its roles and mechanisms (2009)](https://doi.org/10.1146/annurev-genet-102108-134233)
[Higashi TL, et al, A structure-based mechanism for cohesin loading onto chromosomes (2020)](https://doi.org/10.1038/s41586-019-1873-1)
[Michaelis C, Ciosk R, Nasmyth K, Cohesins: chromosomal proteins that prevent premature separation of sister chromatids (1997)](https://doi.org/10.1016/s0092-8674(01)
[Rao SSP, et al, A 3D map of the human genome at kilobase resolution reveals principles of chromatin looping (2014)](https://doi.org/10.1016/j.cell.2014.11.021)
[Watrin E, Peters JM, The cohesin complex is required for the DNA damage-induced G2/M checkpoint (2006)](https://doi.org/10.1016/j.molcel.2006.07.018)
[Deardorff MA, et al, SMC3 mutations in Cornelia de Lange syndrome (2007)](https://doi.org/10.1086/521372)
[Gomperts SN, et al, Cornelia de Lange syndrome and autism spectrum disorder (2009)](https://doi.org/10.1002/ajmg.a.32898)
[Kon A, et al, Recurrent mutations in multiple components of the cohesin complex in myeloid neoplasms (2013)](https://doi.org/10.1038/ng.2731)
[Wendt KS, et al, Cohesin mediates transcriptional insulation of CCCTC-binding factor (2008)](https://doi.org/10.1038/nature06634)
[Kline AD, et al, Diagnosis and management of Cornelia de Lange syndrome: first international consensus statement (2018)](https://doi.org/10.1038/s41576-018-0036-0)Pathway Diagram
The following diagram shows the key molecular relationships involving SMC3 - Structural Maintenance of Chromosomes 3 discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)