PNO1: Partner of NOB1 Homolog, Ribosome Biogenesis Factor
A key regulator of ribosome assembly and RNA processing with implications in cancer and developmental disorders.
Gene Information Card
| Symbol | PNO1 |
|---|---|
| Full Name | Partner of NOB1 Homolog (S. cerevisiae) |
| Gene Type | Protein coding |
| Chromosomal Location | 2p14 |
| NCBI Gene ID | 56902 ncbi.nlm.nih.gov/gene/56902 |
| Ensembl ID | ENSG00000115946 |
| UniProt ID | Q9NRX1 |
| OMIM ID | 618102 |
| HGNC ID | 24976 |
| Aliases | RRP20, bA316L14.1 |
Description
PNO1 (Partner of NOB1 Homolog) encodes a highly conserved RNA-binding protein essential for ribosome biogenesis. It is a component of the pre-40S ribosomal particle and facilitates the final maturation steps of the small ribosomal subunit. PNO1 interacts with NOB1 and other ribosome assembly factors to coordinate pre-rRNA processing. The gene is ubiquitously expressed and its dysregulation has been linked to various cancers and neurodevelopmental disorders.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Neurodevelopmental disorder with hypotonia and brain abnormalities | Loss-of-function mutations impair ribosome maturation, leading to defective protein synthesis in neural progenitors. | ClinVar, OMIM |
| Hepatocellular carcinoma | Overexpression promotes cell proliferation and metastasis via PI3K/AKT pathway activation. | COSMIC, PubMed |
| Colorectal cancer | Upregulation correlates with poor prognosis; PNO1 knockdown reduces tumor growth in vitro. | COSMIC, PubMed |
| Breast cancer | High expression associated with aggressive subtypes and reduced survival. | COSMIC, PubMed |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Testis | 28.5 | High |
| Lymph node | 22.1 | High |
| Bone marrow | 19.8 | High |
| Brain | 12.3 | Medium |
| Liver | 10.7 | Medium |
| Heart | 8.4 | Medium |
| Lung | 7.1 | Low |
| Kidney | 6.5 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HEK293 | 25.2 | Embryonic kidney; high expression |
| HeLa | 22.8 | Cervical carcinoma; high expression |
| HepG2 | 18.5 | Hepatocellular carcinoma; moderate-high |
| MCF7 | 15.3 | Breast cancer; moderate |
| K562 | 12.1 | Leukemia; moderate |
| A549 | 9.4 | Lung cancer; low-moderate |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.1A>G (p.Met1?) | Missense | Rare | Loss of start codon; predicted loss of function |
| c.325C>T (p.Arg109Trp) | Missense | <0.01% | Impaired RNA binding; associated with neurodevelopmental disorder |
| c.502G>A (p.Gly168Arg) | Missense | <0.01% | Reduced protein stability; reported in ClinVar |
| c.634_636del (p.Lys212del) | In-frame deletion | Rare | Disrupts NOB1 interaction; likely pathogenic |
Mutation functional classification
Loss of Function (LOF)
Homozygous or compound heterozygous missense/nonsense mutations in PNO1 cause loss of ribosome biogenesis function, leading to neurodevelopmental phenotypes.
Gain of Function (GOF)
Not well established; overexpression in cancers may act as an oncogenic gain-of-function through enhanced ribosome production.
Dominant Negative (DN)
No confirmed dominant-negative mutations reported; heterozygous truncating variants may exert mild dominant-negative effects in some contexts.
View complete mutation data：
Gene Ontology (GO)
| • RNA binding (GO:0003723) | • Ribosome biogenesis (GO:0042254) |
| • Maturation of SSU-rRNA (GO:0030490) | • Nucleolus (GO:0005730) |
| • Cytoplasm (GO:0005737) | • Pre-ribosome (GO:0030684) |
Pathways
• Ribosome biogenesis in eukaryotes (KEGG: hsa03008)
• rRNA processing in the nucleus and cytosol (Reactome: R-HSA-8868773)
• Major pathway of rRNA processing in the nucleolus and cytosol (Reactome: R-HSA-6791226)
Protein Summary
PNO1 is a 252-amino acid RNA-binding protein localized primarily to the nucleolus. It contains a KH domain that mediates interaction with pre-rRNA and the NOB1 protein. PNO1 is essential for the final cleavage steps of 20S pre-rRNA to mature 18S rRNA, a critical event in small ribosomal subunit assembly. The protein shuttles between the nucleus and cytoplasm, and its expression is cell-cycle regulated. Structural studies show that PNO1 adopts a conserved fold that binds RNA with high affinity. Post-translational modifications include phosphorylation, which may modulate its activity.
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