POLR1B: RNA Polymerase I Subunit B
Essential component of RNA polymerase I complex involved in ribosomal RNA synthesis
Gene Information Card
| Symbol | POLR1B |
|---|---|
| Full Name | RNA Polymerase I Subunit B |
| Gene Type | Protein coding |
| Chromosomal Location | 2q14.1 |
| NCBI Gene ID | 84172 ncbi.nlm.nih.gov/gene/84172 |
| Ensembl ID | ENSG00000115904 |
| UniProt ID | Q9H9Y6 |
| OMIM ID | 602000 |
| HGNC ID | 20454 |
| Aliases | RPA2, RPA2-1, RPA40, POLR1B1, A-40 |
Description
POLR1B encodes the second largest subunit of RNA polymerase I, which synthesizes ribosomal RNA (rRNA) precursors. This subunit is essential for transcription initiation and elongation of rRNA genes. Mutations in POLR1B are associated with Treacher Collins syndrome, a disorder of craniofacial development, due to impaired ribosome biogenesis.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Treacher Collins syndrome | Loss-of-function mutations impair rRNA synthesis, leading to reduced ribosome biogenesis and neural crest cell apoptosis during craniofacial development | ClinVar, OMIM |
| Acrofacial dysostosis | Similar mechanism to Treacher Collins syndrome, with additional limb anomalies | ClinVar, OMIM |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Testis | 12.5 | Medium |
| Thyroid | 10.2 | Medium |
| Brain | 8.9 | Medium |
| Heart | 7.3 | Low |
| Liver | 6.1 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HeLa | 15.0 | High expression |
| HEK293 | 12.3 | Medium expression |
| K562 | 9.8 | Medium expression |
| A549 | 8.5 | Low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.331C>T (p.Arg111*) | Nonsense | <0.1% | Loss of function; associated with Treacher Collins syndrome |
| c.1045G>A (p.Gly349Arg) | Missense | <0.1% | Dominant negative effect; disrupts RNA polymerase I assembly |
| c.1582C>T (p.Arg528Trp) | Missense | <0.1% | Loss of function; reduced rRNA transcription |
Mutation functional classification
Loss of Function (LOF)
Nonsense and frameshift mutations leading to truncated protein or nonsense-mediated decay; missense mutations impairing catalytic activity or subunit interaction
Gain of Function (GOF)
Not reported
Dominant Negative (DN)
Missense mutations (e.g., p.Gly349Arg) that disrupt complex assembly but allow mutant protein to compete with wild-type
View complete mutation data：
Gene Ontology (GO)
| • DNA-directed 5'-3' RNA polymerase activity | • ribosomal RNA transcription |
| • nucleolus | • RNA polymerase I complex |
| • transcription initiation from RNA polymerase I promoter | • transcription elongation from RNA polymerase I promoter |
Pathways
• RNA polymerase I transcription
• rRNA processing
• Ribosome biogenesis
Protein Summary
POLR1B encodes the 40 kDa subunit (RPA2) of RNA polymerase I, which is responsible for transcribing ribosomal RNA genes. The protein contains a conserved RNA polymerase domain and interacts with other subunits to form the active enzyme complex. It is localized to the nucleolus and is essential for ribosome biogenesis. Mutations in POLR1B cause Treacher Collins syndrome by reducing rRNA synthesis and triggering apoptosis in neural crest cells.
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