POLR3A
RNA Polymerase III Subunit A
Gene Information Card
| Symbol | POLR3A |
|---|---|
| Full Name | RNA Polymerase III Subunit A |
| Gene Type | Protein coding |
| Chromosomal Location | 10q22.3 |
| NCBI Gene ID | 11128 ncbi.nlm.nih.gov/gene/11128 |
| Ensembl ID | ENSG00000148606 |
| UniProt ID | O14802 |
| OMIM ID | 614258 |
| HGNC ID | 30074 |
| Aliases | RPC1, RPC155, RPOL3C, hRPC155 |
Description
POLR3A encodes the largest catalytic subunit of RNA polymerase III, which transcribes small non-coding RNAs such as tRNAs, 5S rRNA, U6 snRNA, and other small RNAs. This subunit contains the active site for RNA synthesis and is essential for polymerase assembly and function. Mutations in POLR3A cause hypomyelinating leukodystrophy and related neurological disorders.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Hypomyelinating leukodystrophy 7 (HLD7) | Loss-of-function mutations impair RNA polymerase III activity, reducing transcription of small RNAs needed for myelin formation. | OMIM #607694 |
| Leukodystrophy, hypomyelinating, 7, with or without oligodontia and/or hypogonadotropic hypogonadism | Same mechanism as HLD7; additional features due to broader transcriptional defects. | OMIM #607694 |
| Cerebellar ataxia, hypomyelination, and dental abnormalities | Mutations disrupt RNA Pol III function, affecting cerebellar development and myelination. | OMIM #614258 |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Brain | 8.2 | Medium |
| Testis | 6.5 | Medium |
| Heart | 5.1 | Low |
| Liver | 4.8 | Low |
| Kidney | 4.3 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HEK 293 | 9.1 | High expression |
| HeLa | 7.8 | Medium expression |
| K562 | 6.4 | Medium expression |
| HepG2 | 5.9 | Low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.2554A>G (p.Met852Val) | Missense | Rare | Reduced RNA Pol III activity; associated with HLD7 |
| c.3337C>T (p.Arg1113*) | Nonsense | Rare | Loss of function; truncation of catalytic domain |
| c.1771-6C>G | Splice site | Rare | Aberrant splicing; reduced protein expression |
Mutation functional classification
Loss of Function (LOF)
Most POLR3A mutations are loss-of-function, leading to reduced RNA Pol III activity and impaired transcription of small non-coding RNAs.
Gain of Function (GOF)
No gain-of-function mutations have been reported for POLR3A.
Dominant Negative (DN)
Some missense mutations may exert dominant-negative effects by disrupting polymerase complex assembly, though evidence is limited.
View complete mutation data：
Gene Ontology (GO)
| • DNA-directed 5'-3' RNA polymerase activity | • RNA polymerase III activity |
| • nucleus | • nucleoplasm |
| • cytoplasm | • transcription of RNA polymerase III |
Pathways
• RNA polymerase III transcription
• tRNA processing
• 5S rRNA transcription
Protein Summary
POLR3A encodes the 155 kDa catalytic subunit of RNA polymerase III. This subunit contains the active site for RNA synthesis and is essential for the transcription of small non-coding RNAs, including tRNAs, 5S rRNA, and U6 snRNA. The protein localizes to the nucleus and interacts with other polymerase subunits to form the functional enzyme complex.
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