RIOK2
RIO Kinase 2: A Conserved Atypical Kinase Involved in Ribosome Biogenesis and Cell Cycle Control
Gene Information Card
| Symbol | RIOK2 |
|---|---|
| Full Name | RIO Kinase 2 |
| Gene Type | Protein coding |
| Chromosomal Location | 5q15 |
| NCBI Gene ID | 55781 ncbi.nlm.nih.gov/gene/55781 |
| Ensembl ID | ENSG00000164332 |
| UniProt ID | Q9BVS4 |
| OMIM ID | 616513 |
| HGNC ID | 23299 |
| Aliases | RIO2, RIO kinase 2, RIO2 kinase |
Description
RIOK2 (RIO Kinase 2) is a member of the atypical RIO family of serine/threonine kinases, which are conserved from archaea to humans. Unlike typical eukaryotic protein kinases, RIO kinases lack the canonical DFG motif in the activation loop. RIOK2 is essential for ribosome biogenesis, specifically for the processing of 20S pre-rRNA to mature 18S rRNA, and is also implicated in cell cycle progression, particularly at the G1/S transition. The gene is located on chromosome 5q15 and encodes a 552-amino acid protein. RIOK2 is widely expressed in human tissues and is overexpressed in several cancers, where it may contribute to tumorigenesis by promoting ribosome production and cell proliferation.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Cancer (general) | Overexpression of RIOK2 promotes ribosome biogenesis and cell cycle progression, leading to enhanced proliferation. | COSMIC; literature (PMID: 25944712) |
| Colorectal cancer | RIOK2 is upregulated and associated with poor prognosis; knockdown reduces cell growth. | COSMIC; literature (PMID: 25944712) |
| Hepatocellular carcinoma | RIOK2 overexpression correlates with aggressive tumor features and may serve as a prognostic marker. | COSMIC; literature (PMID: 25944712) |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Testis | 12.5 | Medium |
| Bone marrow | 10.2 | Medium |
| Lymph node | 8.9 | Medium |
| Brain | 6.3 | Low |
| Liver | 5.1 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HeLa | 14.3 | Cervical cancer cell line |
| HEK293 | 11.8 | Embryonic kidney cell line |
| HCT116 | 9.7 | Colorectal cancer cell line |
| MCF7 | 7.2 | Breast cancer cell line |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| p.Glu322Lys | Missense | <0.1% | Unknown; likely benign |
| p.Arg370Trp | Missense | <0.1% | Unknown; likely benign |
| p.Leu400Pro | Missense | <0.1% | Unknown; likely benign |
Mutation functional classification
Loss of Function (LOF)
No confirmed loss-of-function mutations reported in COSMIC or ClinVar.
Gain of Function (GOF)
No confirmed gain-of-function mutations reported; overexpression is the primary oncogenic mechanism.
Dominant Negative (DN)
No dominant-negative mutations described.
View complete mutation data：
Gene Ontology (GO)
| • ATP binding | • protein serine/threonine kinase activity |
| • rRNA processing | • ribosome biogenesis |
| • cell cycle | • G1/S transition of mitotic cell cycle |
Pathways
• Ribosome biogenesis in eukaryotes
• rRNA processing
Protein Summary
RIOK2 is a 552-amino acid atypical serine/threonine kinase localized predominantly in the nucleus and nucleolus. It contains an N-terminal RIO domain responsible for kinase activity and a C-terminal domain involved in protein-protein interactions. The protein is essential for the cleavage of 20S pre-rRNA to generate mature 18S rRNA, a critical step in small ribosomal subunit assembly. RIOK2 also interacts with cell cycle regulators such as CDK2 and cyclin E, facilitating G1/S transition. Its overexpression in multiple cancer types suggests a role in oncogenesis by enhancing ribosome production and cell proliferation.
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