BDP1: B Double Prime 1, Subunit of RNA Polymerase III Transcription Initiation Factor IIIB
Essential component of TFIIIB complex for RNA polymerase III-mediated transcription of small non-coding RNAs
Gene Information Card
| Symbol | BDP1 |
|---|---|
| Full Name | B double prime 1, subunit of RNA polymerase III transcription initiation factor IIIB |
| Gene Type | Protein coding |
| Chromosomal Location | 5q13.2 |
| NCBI Gene ID | 55814 ncbi.nlm.nih.gov/gene/55814 |
| Ensembl ID | ENSG00000145734 |
| UniProt ID | Q9H3Z4 |
| OMIM ID | 607012 |
| HGNC ID | 1360 |
| Aliases | TFIIIB150, BDP, hBDP1, KIAA1241 |
Description
BDP1 encodes the B double prime 1 protein, a key component of the transcription factor IIIB (TFIIIB) complex. TFIIIB is essential for transcription initiation by RNA polymerase III (Pol III), which synthesizes small non-coding RNAs including tRNAs, 5S rRNA, U6 snRNA, and other regulatory RNAs. BDP1 directly interacts with TATA-binding protein (TBP) and BRF1/BRF2 to form the TFIIIB complex, facilitating promoter recognition and Pol III recruitment. The gene is located on chromosome 5q13.2 and is expressed ubiquitously.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Hereditary hearing loss (autosomal recessive deafness 86) | Biallelic loss-of-function mutations in BDP1 disrupt TFIIIB complex assembly, impairing Pol III transcription of tRNAs and other small RNAs essential for cochlear hair cell function. | ClinVar; OMIM #617641 |
| Charcot-Marie-Tooth disease (recessive intermediate type) | Missense mutations in BDP1 cause reduced TFIIIB activity, leading to peripheral nerve degeneration due to impaired tRNA and snRNA synthesis. | OMIM #618184 |
| Cancer (multiple types) | Somatic mutations and altered BDP1 expression affect Pol III transcription of non-coding RNAs, promoting uncontrolled cell proliferation. Overexpression observed in breast, lung, and colorectal cancers. | COSMIC; PubMed studies |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Brain | 10.2 | Medium |
| Heart | 8.5 | Medium |
| Liver | 12.1 | Medium |
| Kidney | 9.8 | Medium |
| Testis | 15.3 | High |
| Lung | 7.4 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HEK293 | 11.5 | Embryonic kidney cells |
| HeLa | 9.2 | Cervical carcinoma cells |
| K562 | 8.8 | Leukemia cells |
| HepG2 | 10.1 | Hepatocellular carcinoma cells |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.2407C>T (p.Arg803Ter) | Nonsense | Rare | Loss of function; associated with deafness |
| c.1234G>A (p.Gly412Arg) | Missense | Rare | Reduced TFIIIB activity; Charcot-Marie-Tooth disease |
| c.3456_3457del (p.Glu1152Aspfs*5) | Frameshift | Rare | Loss of function; hearing loss |
| c.5678A>G (p.Tyr1893Cys) | Missense | Somatic | Unknown functional effect; found in cancer |
Mutation functional classification
Loss of Function (LOF)
Nonsense and frameshift mutations leading to truncated BDP1 protein or nonsense-mediated decay, impairing TFIIIB complex formation and Pol III transcription.
Gain of Function (GOF)
Not reported; no activating mutations described in literature.
Dominant Negative (DN)
Not established; BDP1 mutations are typically recessive or somatic with unclear dominant-negative effects.
View complete mutation data：
Gene Ontology (GO)
Pathways
• RNA polymerase III transcription initiation (Reactome R-HSA-76061)
• TFIIIB complex assembly (Reactome R-HSA-76066)
• Gene expression (Transcription) (Reactome R-HSA-74160)
Protein Summary
BDP1 (B double prime 1) is a 2204-amino acid protein that serves as the largest subunit of the TFIIIB complex. It contains a conserved B-block binding domain and interacts with TBP and BRF1/BRF2 to recruit RNA polymerase III to target gene promoters. The protein is essential for transcription of small non-coding RNAs, including tRNAs, 5S rRNA, and U6 snRNA. BDP1 is ubiquitously expressed with highest levels in testis. Mutations cause autosomal recessive deafness and Charcot-Marie-Tooth disease, while altered expression is linked to cancer.
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