SNRPA1: Small Nuclear Ribonucleoprotein Polypeptide A'
A core component of the U1, U2, U4, and U5 snRNPs involved in pre-mRNA splicing
Gene Information Card
| Symbol | SNRPA1 |
|---|---|
| Full Name | Small Nuclear Ribonucleoprotein Polypeptide A' |
| Gene Type | Protein coding |
| Chromosomal Location | 15q26.3 |
| NCBI Gene ID | 6626 ncbi.nlm.nih.gov/gene/6626 |
| Ensembl ID | ENSG00000137809 |
| UniProt ID | P09661 |
| OMIM ID | 603521 |
| HGNC ID | 11151 |
| Aliases | U1-A, U2-A', Mud1, RNPA1, U1 snRNP A, U2 snRNP A' |
Description
SNRPA1 encodes the A' protein, a component of the U1, U2, U4, and U5 small nuclear ribonucleoproteins (snRNPs). These snRNPs are essential for pre-mRNA splicing, the process by which introns are removed and exons joined to form mature mRNA. The protein contains two RNA recognition motifs (RRMs) and binds directly to stem-loop II of U1 snRNA and stem-loop III of U2 snRNA. SNRPA1 is ubiquitously expressed and plays a critical role in spliceosome assembly and function.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Systemic lupus erythematosus (SLE) | Autoantibodies against U1 snRNP components, including SNRPA1, are a hallmark of SLE; immune complexes contribute to tissue damage. | ClinVar, OMIM |
| Mixed connective tissue disease (MCTD) | High-titer anti-U1 RNP antibodies target SNRPA1 and other snRNP proteins; associated with clinical overlap of SLE, scleroderma, and polymyositis. | OMIM, literature |
| Cancer (various) | Altered splicing factor expression, including SNRPA1, can drive aberrant splicing and tumorigenesis; overexpression reported in some cancers. | COSMIC, literature |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Testis | 28.5 | High |
| Lymph node | 22.3 | High |
| Spleen | 20.1 | High |
| Brain | 12.4 | Medium |
| Liver | 9.8 | Medium |
| Heart | 8.2 | Medium |
| Kidney | 7.5 | Low |
| Lung | 6.9 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HEK 293 | 18.2 | High expression |
| HeLa | 15.7 | High expression |
| K562 | 12.1 | Medium expression |
| HepG2 | 10.5 | Medium expression |
| A549 | 9.3 | Medium expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.1A>G (p.Met1?) | Missense | Rare | Likely loss of start codon; predicted to abolish protein expression |
| c.214G>A (p.Gly72Arg) | Missense | Rare | Located in RRM1; may reduce RNA binding affinity |
| c.487C>T (p.Arg163Trp) | Missense | Rare | Located in RRM2; potential impact on snRNA interaction |
| c.631_632insA (p.Thr211Asnfs*5) | Frameshift | Rare | Premature stop; likely loss of function |
Mutation functional classification
Loss of Function (LOF)
Frameshift and start-loss mutations are predicted to cause loss of function by truncating or preventing protein synthesis.
Gain of Function (GOF)
No gain-of-function mutations have been reported for SNRPA1.
Dominant Negative (DN)
No dominant-negative mutations have been characterized for SNRPA1.
View complete mutation data：
Gene Ontology (GO)
Pathways
• Spliceosome (KEGG hsa03040)
• mRNA Splicing - Major Pathway (Reactome R-HSA-72163)
• Processing of Capped Intron-Containing Pre-mRNA (Reactome R-HSA-72203)
Protein Summary
SNRPA1 encodes a 31.5 kDa protein (255 amino acids) with two RNA recognition motifs (RRMs). It is a core component of U1, U2, U4, and U5 snRNPs, binding directly to U1 snRNA stem-loop II and U2 snRNA stem-loop III. The protein is essential for stable snRNP assembly and spliceosome function. Autoantibodies against SNRPA1 are diagnostic markers for mixed connective tissue disease and systemic lupus erythematosus. Somatic mutations are rare but may contribute to splicing dysregulation in cancer.
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