TFB1M: Transcription Factor B1, Mitochondrial
Mitochondrial transcription factor essential for mtDNA expression and oxidative phosphorylation
Gene Information Card
| Symbol | TFB1M |
|---|---|
| Full Name | Transcription Factor B1, Mitochondrial |
| Gene Type | Protein coding |
| Chromosomal Location | 6q25.3 |
| NCBI Gene ID | 51106 ncbi.nlm.nih.gov/gene/51106 |
| Ensembl ID | ENSG00000112210 |
| UniProt ID | Q8IYQ7 |
| OMIM ID | 607033 |
| HGNC ID | 11723 |
| Aliases | CGI-75, mtTFB1, S-adenosylmethionine-dependent methyltransferase |
Description
TFB1M encodes a mitochondrial transcription factor that is a component of the mitochondrial transcription initiation complex. It binds to the mitochondrial RNA polymerase (POLRMT) and facilitates promoter recognition and transcription initiation. Additionally, TFB1M functions as an S-adenosylmethionine-dependent methyltransferase, modifying mitochondrial 12S rRNA at position G1219, which is critical for mitochondrial ribosome assembly and translation. Defects in TFB1M are associated with mitochondrial dysfunction and oxidative phosphorylation disorders.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Combined oxidative phosphorylation deficiency 15 (COXPD15) | Loss-of-function mutations impair mitochondrial transcription and translation, leading to reduced complex I and IV activity | OMIM #614946 |
| Mitochondrial encephalopathy | Disrupted mtDNA expression due to TFB1M deficiency affects neuronal energy metabolism | Case reports in literature |
| Sensorineural hearing loss | Mutations in TFB1M may predispose to aminoglycoside-induced ototoxicity via altered mitochondrial translation | ClinVar |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Heart | 12.5 | Medium |
| Skeletal muscle | 10.2 | Medium |
| Liver | 8.1 | Low |
| Brain | 7.4 | Low |
| Kidney | 6.9 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HeLa | 15.3 | Cervical cancer cell line |
| HEK293 | 14.1 | Embryonic kidney cells |
| HepG2 | 11.8 | Hepatocellular carcinoma |
| K562 | 9.5 | Leukemia cell line |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.494G>A (p.Arg165His) | Missense | Rare | Impaired methyltransferase activity and mitochondrial translation |
| c.1A>G (p.Met1Val) | Start loss | Very rare | Loss of protein expression |
| c.748C>T (p.Arg250*) | Nonsense | Rare | Premature truncation, loss of function |
Mutation functional classification
Loss of Function (LOF)
Missense and nonsense mutations that reduce or abolish methyltransferase activity or transcription factor function, leading to mitochondrial translation defects.
Gain of Function (GOF)
Not reported for TFB1M.
Dominant Negative (DN)
Not reported; TFB1M mutations are typically recessive.
View complete mutation data：
Gene Ontology (GO)
| • mitochondrion (GO:0005739) | • mitochondrial transcription (GO:0006390) |
| • N-methyltransferase activity (GO:0008170) | • RNA binding (GO:0003723) |
| • fibrillar center (GO:0001650) |
Pathways
• Mitochondrial transcription initiation (Reactome: R-HSA-163200)
• Mitochondrial translation (Reactome: R-HSA-5368287)
• Oxidative phosphorylation (KEGG: hsa00190)
Protein Summary
TFB1M is a 398-amino acid protein localized to the mitochondrial matrix. It contains a methyltransferase domain and a transcription factor domain. As part of the mitochondrial transcription initiation complex, it interacts with POLRMT and TFAM to initiate transcription of mtDNA. Its methyltransferase activity modifies 12S rRNA, essential for mitochondrial ribosome assembly and efficient translation of mtDNA-encoded subunits of the oxidative phosphorylation system.
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