SF3B3: Splicing Factor 3b Subunit 3
A core component of the U2 snRNP spliceosome complex involved in pre-mRNA splicing and cancer-associated splicing alterations.
Gene Information Card
| Symbol | SF3B3 |
|---|---|
| Full Name | Splicing Factor 3b Subunit 3 |
| Gene Type | Protein coding |
| Chromosomal Location | 16q22.1 |
| NCBI Gene ID | 23450 ncbi.nlm.nih.gov/gene/23450 |
| Ensembl ID | ENSG00000189091 |
| UniProt ID | Q15393 |
| OMIM ID | 605592 |
| HGNC ID | 10770 |
| Aliases | SAP130, SF3b130, RSE1 |
Description
SF3B3 encodes a subunit of the splicing factor 3b complex, which is part of the U2 small nuclear ribonucleoprotein (snRNP). This complex is essential for pre-mRNA splicing by recognizing the branch point sequence during spliceosome assembly. SF3B3 interacts with other spliceosomal components and is implicated in RNA processing regulation. Mutations and altered expression of SF3B3 have been associated with various cancers, including breast, lung, and hematologic malignancies.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Breast cancer | Altered splicing of oncogenes and tumor suppressors due to SF3B3 overexpression | COSMIC, ClinVar |
| Lung adenocarcinoma | SF3B3 mutations lead to aberrant splicing of cell cycle genes | COSMIC, NCBI |
| Myelodysplastic syndromes | Somatic mutations in SF3B3 (rare) may affect spliceosome function | ClinVar, COSMIC |
| Colorectal cancer | SF3B3 upregulation correlates with poor prognosis | NCBI, COSMIC |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Testis | 25.3 | High |
| Lymph node | 18.7 | Medium |
| Bone marrow | 15.2 | Medium |
| Brain cortex | 12.1 | Medium |
| Liver | 8.4 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HEK293 | 22.5 | High expression |
| HeLa | 19.8 | High expression |
| MCF7 | 16.3 | Medium expression |
| A549 | 14.7 | Medium expression |
| K562 | 12.1 | Medium expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.1286A>G (p.Asn429Ser) | Missense | <0.1% in COSMIC | Unknown functional effect |
| c.2143C>T (p.Arg715Trp) | Missense | <0.1% in COSMIC | Potential loss of splicing fidelity |
| c.3010G>A (p.Glu1004Lys) | Missense | <0.1% in COSMIC | Reported in lung adenocarcinoma |
Mutation functional classification
Loss of Function (LOF)
Rare missense mutations may impair SF3B3 interaction with other spliceosomal proteins, reducing splicing efficiency.
Gain of Function (GOF)
Not well characterized; overexpression in cancers suggests possible gain-of-function role in splicing dysregulation.
Dominant Negative (DN)
No evidence for dominant-negative effects currently.
View complete mutation data：
Gene Ontology (GO)
| • RNA splicing | • mRNA processing |
| • spliceosomal complex assembly | • U2 snRNP binding |
| • nucleus |
Pathways
• mRNA Splicing - Major Pathway
• Spliceosome (KEGG hsa03040)
• Processing of Capped Intron-Containing Pre-mRNA
Protein Summary
SF3B3 (SAP130) is a 130 kDa protein that forms part of the SF3b complex within the U2 snRNP. It contains a ubiquitin-like domain and is involved in recognizing the branch point adenosine during pre-mRNA splicing. The protein localizes to the nucleus and is essential for spliceosome assembly. Structural studies show it interacts with SF3B1 and SF3B2 to stabilize the complex. Post-translational modifications include phosphorylation, which may regulate its activity.
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