Affinage

PNO1

RNA-binding protein PNO1 · UniProt Q9NRX1

Length
252 aa
Mass
27.9 kDa
Annotated
2026-06-10
23 papers in source corpus 17 papers cited in narrative 17 extracted findings
Cross-family judge vs UniProt: tie faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PNO1 is a KH-domain RNA-binding protein essential for small ribosomal subunit biogenesis, acting within 90S/pre-40S pre-ribosomal particles to drive early pre-rRNA cleavages at sites A1/A2 that generate mature 18S rRNA (PMID:12736301). The protein localizes to the nucleus and concentrates in nucleoli, with residues 92–230 (rather than the KH domain alone) conferring nucleolar retention (PMID:15497447). Loss of PNO1 reduces 18S rRNA, 40S/60S subunits, and 80S ribosomes and lowers global protein synthesis, and it functions together with NOB1 in maturation of the 40S small subunit (PMID:30862720, PMID:40157618). PNO1 is required for early development, as homozygous knockout causes pre-compaction embryonic lethality in mice, and the protein also associates with large 20S–26S complexes implicated in proteasome assembly (PMID:23029399, PMID:39414903). In cancer, PNO1 is broadly tumor-promoting: its depletion induces nucleolar stress that blocks MDM2-mediated p53 degradation, elevating p53 and p21 (PMID:30862720), impairs proteasome activity and stabilizes the CDK inhibitor p27/CDKN1B (PMID:39414903), and it interacts physically with THBS1 to activate FAK/Akt signaling (PMID:33664245). PNO1 expression is controlled transcriptionally—repressed by EBF1 and activated by MYC and E2F6 (PMID:30862720, PMID:32676457, PMID:33664245, PMID:35870038)—and post-transcriptionally suppressed by miR-340-5p and miR-326 (PMID:32483111, PMID:39414903).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 2003 High

    Established the core molecular function of PNO1 by showing its yeast ortholog RRP20 is required for the early pre-rRNA cleavages that produce 18S rRNA.

    Evidence Northern blotting, primer extension, and KH-domain point mutagenesis in S. cerevisiae

    PMID:12736301

    Open questions at the time
    • Did not resolve whether the KH domain directly binds pre-rRNA or acts via partner recruitment
    • Human protein function not yet tested
  2. 2004 Medium

    Defined where human PNO1 acts by mapping a discrete nucleolar-retention region, showing the KH domain alone is insufficient for localization.

    Evidence GFP-fusion deletion mapping of 13 constructs in mammalian cells

    PMID:15497447

    Open questions at the time
    • No identification of the binding partner or RNA element mediating nucleolar retention
    • Single-lab localization without endogenous validation
  3. 2012 Medium

    Demonstrated PNO1 is organismally essential and revealed a possible non-ribosomal complex association distinct from mature proteasomes and ribosomes.

    Evidence Pno1 knockout mouse with embryo development assay plus density gradient fractionation

    PMID:23029399

    Open questions at the time
    • Identity of the 20S–26S complexes left undefined
    • Lethality phenotype not mechanistically tied to a specific pathway
  4. 2019 High

    Connected PNO1's ribosome-biogenesis role to tumor cell control, showing depletion triggers nucleolar stress that stabilizes p53 via MDM2 inhibition.

    Evidence shRNA knockdown, ribosome fractionation, p53 KO and PFT-α rescue, promoter assay, xenografts in CRC cells

    PMID:30862720

    Open questions at the time
    • EBF1–PNO1 regulation shown by promoter assay but direct EBF1 binding not mapped
    • p53-independent contributions not fully separated
  5. 2020 Medium

    Defined upstream regulatory inputs (EBF1 repression, miR-340-5p) and a downstream Notch/EMT output, broadening PNO1's oncogenic circuitry.

    Evidence EBF1 transduction with promoter assay; miR-340-5p 3'UTR reporter and rescue; invasion assays in CRC and lung adenocarcinoma

    PMID:32483111 PMID:32676457

    Open questions at the time
    • Whether Notch modulation is direct or secondary to ribosome biogenesis loss is unresolved
    • Single-lab pathway placements
  6. 2021 Medium

    Identified PNO1's first named direct physical partner (THBS1) and the MYC transcriptional activation input, linking PNO1 to FAK/Akt signaling.

    Evidence Co-IP for PNO1–THBS1, THBS1 siRNA rescue, MYC→PNO1 promoter assay, FAK/Akt Western blots in glioma

    PMID:33664245

    Open questions at the time
    • Reciprocal Co-IP / direct binding interface for THBS1 not defined
    • Mechanism connecting THBS1 to FAK/Akt not established at molecular level
  7. 2022 Medium

    Added the E2F6 transcriptional activator to PNO1's regulatory network and linked PNO1 depletion to G2/M arrest with CCNB1/CDK1 loss.

    Evidence RIP, RNA pull-down, FISH for E2F6–PNO1 promoter binding; flow cytometry and Western blot in TNBC

    PMID:35445733 PMID:35870038

    Open questions at the time
    • Cell-cycle marker changes correlative, not mechanistically linked
    • Direct vs indirect control of CCNB1/CDK1 unresolved
  8. 2024 Medium

    Extended PNO1 function to proteasome assembly and p27 turnover, and reaffirmed its NOB1 partnership in 40S maturation.

    Evidence shRNA knockdown, proteasome activity assay, p27 knockdown rescue, miR-326 CDS reporter; plus literature review of NOB1 collaboration

    PMID:39143880 PMID:39414903

    Open questions at the time
    • Mechanism by which PNO1 supports proteasome assembly is undefined
    • NOB1 statement derives from review, not new primary data
  9. 2025 Medium

    Used unbiased proximity proteomics to map PNO1's interaction landscape and confirmed translation-machinery partners EIF4B and EIF4G2.

    Evidence TurboID proximity labeling, mass spectrometry, Co-IP, immunofluorescence

    PMID:40157618

    Open questions at the time
    • Functional consequence of EIF4B/EIF4G2 interactions untested
    • Extent of overlap vs divergence from NOB1 interactome not functionally resolved
  10. 2025 Low

    Expanded the catalog of oncogenic signaling cascades downstream of PNO1 to AKT/Wnt/β-catenin and NF-κB-driven stemness.

    Evidence siRNA/shRNA knockdown, RNA-seq, pharmacological rescue (AKT inhibitors, JSH-23), sphere assays in ovarian and breast cancer

    PMID:40113869 PMID:40971713

    Open questions at the time
    • Pathway assignments rest on Western blot and inhibitor rescue without direct binding
    • Whether these are distinct mechanisms or convergent consequences of impaired ribosome biogenesis is unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • It remains unresolved whether PNO1's many cancer-signaling phenotypes are direct molecular activities or downstream consequences of its core role in 40S ribosome biogenesis and translation.
  • No structural model of PNO1 in the human pre-40S particle reported in the corpus
  • Direct RNA targets of human PNO1 not mapped
  • Causal hierarchy among p53, proteasome, and signaling effects undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003723 RNA binding 2
Localization
GO:0005730 nucleolus 2 GO:0005634 nucleus 1
Pathway
R-HSA-392499 Metabolism of proteins 2 R-HSA-8953854 Metabolism of RNA 2
Complex memberships
90S/pre-40S pre-ribosomal particle

Evidence

Reading pass · 17 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2003 Yeast RRP20 (ortholog of human PNO1) is a nucleolar protein required for pre-18S rRNA processing; a Gly235Asp mutation in its KH-type RNA-binding domain causes marked deficiency in 18S rRNA production by impairing early pre-rRNA cleavages at sites A1 and A2, leading to accumulation of a 22S dead-end processing product. RRP20 is present in 90S pre-ribosomal particles. Northern blotting, primer extension analysis, point mutagenesis, in S. cerevisiae Nucleic acids research High 12736301
2004 Human PNO1 protein (~35 kDa) localizes to the nucleus and specifically to nucleoli; deletion analysis showed that residues 92–230 are solely responsible for nucleolar retention, and the KH domain alone is insufficient for this localization. GFP fusion expression and subcellular localization of 13 deletion constructs in mammalian cells, Western blot DNA sequence : the journal of DNA sequencing and mapping Medium 15497447
2012 Homozygous Pno1 knockout in mice causes early embryonic lethality with arrest before the compaction stage, demonstrating that Pno1 is essential for early development. Density gradient fractionation showed that overexpressed tagged Pno1 exists in large complexes with sedimentation rates between 20S and 26S, distinct from mature 26S proteasomes, 40S, and 60S ribosomal subunits. Gene knockout mouse generation, ex vivo embryo development assay, density gradient fractionation PloS one Medium 23029399
2019 PNO1 knockdown in colorectal cancer cells (HCT116) decreased levels of 18S rRNA, 40S and 60S ribosomal subunits, and 80S ribosomes, and reduced global protein synthesis; this increased nucleolar stress and inhibited MDM2-mediated ubiquitination and p53 degradation, resulting in p53 and p21 upregulation. EBF1 suppresses PNO1 promoter activity and reduces PNO1 mRNA and protein levels. shRNA knockdown, ribosome fractionation, Western blot, luciferase promoter assay, p53 knockout rescue, p53 inhibitor PFT-α rescue, in vitro and xenograft in vivo experiments Cancer research High 30862720
2019 PNO1 knockdown in hepatocellular carcinoma cells suppressed tumor growth and metastasis and significantly reduced AKT/mTOR signaling, implicating PNO1 in activation of this pathway. Lentiviral shRNA knockdown, Western blot, in vitro and xenograft in vivo experiments Medical science monitor Low 31568401
2020 EBF1 overexpression in colorectal cancer cells downregulates PNO1 mRNA and protein expression and transcriptional activity, while upregulating p53 and p21 proteins, suppressing cell growth and inducing apoptosis. Lentiviral transduction of EBF1, luciferase promoter assay for PNO1 transcriptional activity, Western blot, in vitro and in vivo assays Frontiers in oncology Medium 32676457
2020 miR-340-5p directly binds the 3′ UTR of PNO1 mRNA and represses its expression; PNO1 knockdown inhibits the Notch signaling pathway, which in turn modulates epithelial–mesenchymal transition (EMT) in lung adenocarcinoma cells. Luciferase 3′ UTR reporter assay, miRNA overexpression/knockdown rescue experiments, in vitro invasion and proliferation assays, in vivo xenograft Oncogenesis Medium 32483111
2021 PNO1 physically interacts with THBS1, and simultaneous silencing of THBS1 attenuates or reverses the pro-tumorigenic effects of PNO1 overexpression in glioma cells; PNO1 activates FAK/Akt signaling downstream of this interaction. MYC overexpression increases PNO1 promoter activity, placing MYC upstream of PNO1. Co-immunoprecipitation (PNO1–THBS1 interaction), THBS1 siRNA rescue, luciferase promoter assay for MYC→PNO1, Western blot for FAK/Akt, in vitro and in vivo assays Cell death & disease Medium 33664245
2021 PNO1 promotes hepatocellular carcinoma progression through the MAPK signaling pathway, as demonstrated by RNA-seq analysis combined with functional experiments following PNO1 overexpression and knockdown, and associated modulation of autophagy and apoptosis. RNA-seq, Western blot for MAPK pathway components, overexpression/knockdown in vitro and in vivo Cell death & disease Low 34050137
2021 PNO1 knockdown in esophageal cancer cells downregulates CTNNB1 (β-catenin) among other proteins, and overexpression of CTNNB1 reverses the anti-proliferative and pro-apoptotic effects of PNO1 knockdown, placing CTNNB1 downstream of PNO1. shRNA knockdown, CTNNB1 overexpression rescue, Western blot, in vitro proliferation and apoptosis assays Oncology reports Low 33864661
2022 PNO1 knockdown in triple-negative breast cancer cells arrests cell cycle at G2/M phase and downregulates cyclin B1 (CCNB1) and CDK1 protein expression; PNO1 expression is positively correlated with CDK1 and CCNB1 in patient samples. Lentiviral shRNA knockdown, flow cytometry cell-cycle analysis, Western blot, in vitro and xenograft in vivo experiments Oncology reports Low 35445733
2022 The transcription factor E2F6 binds the PNO1 promoter and upregulates PNO1 expression; this is part of a circ_0004676/miR-377-3p/E2F6/PNO1 regulatory axis in triple-negative breast cancer. RIP assay, RNA pull-down, FISH, RT-qPCR, Western blot for promoter binding of E2F6 to PNO1 Cell biology and toxicology Medium 35870038
2024 PNO1 knockdown suppresses CRC cell growth, proteasome activities and assembly, and inhibits CDKN1B/p27Kip1 (p27) degradation via the proteasome; p27 knockdown partially rescues the growth inhibition caused by PNO1 knockdown, placing PNO1 upstream of proteasome assembly and p27 stability. miR-326 directly targets the CDS region of PNO1 mRNA to suppress its protein expression and thereby reduce proteasome activity. shRNA knockdown, miR-326 overexpression, proteasome activity assay, Western blot for p27, luciferase/reporter assay for miR-326 binding, rescue by p27 knockdown Scientific reports Medium 39414903
2024 PNO1 is described as collaborating with NOB1 in the maturation of 20S pre-rRNA into functional 18S rRNA and in maturation of the 40S ribosomal small subunit; PNO1 and NOB1 are positioned within the pre-40S subunit. Review/summary of existing literature (no new direct experiment reported in this abstract) Current pharmaceutical design Low 39143880
2025 PNO1 and NOB1 have distinct subcellular localizations as shown by immunofluorescence; proximity labeling (TurboID) identified 871 proximal proteins for PNO1, with 663 overlapping with NOB1 proximal proteins. Co-IP experiments confirmed that PNO1 interacts with translation-related proteins EIF4B and EIF4G2. TurboID proximity labeling, mass spectrometry, co-immunoprecipitation (Co-IP), immunofluorescence Gene Medium 40157618
2025 PNO1 silencing in ovarian cancer cells decreases p-AKT, GSK-3β, and active β-catenin protein levels, and AKT signaling pathway inhibitors counteract the oncogenic effects of PNO1-activated Wnt/β-catenin signaling, placing PNO1 upstream of the AKT/Wnt/β-catenin pathway. siRNA knockdown, Western blot for AKT/Wnt pathway components, AKT inhibitor pharmacological rescue, xenograft in vivo assay Scientific reports Low 40113869
2025 PNO1 promotes breast cancer stem-like properties through activation of the NF-κB signaling pathway; JSH-23 (NF-κB inhibitor) suppresses these PNO1-dependent stemness effects. shRNA knockdown, RNA-seq, sphere-formation assay, Western blot, flow cytometry, pharmacological inhibition (JSH-23), in vitro and in vivo Stem cells (Dayton, Ohio) Low 40971713

Source papers

Stage 0 corpus · 23 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2019 EBF1-Mediated Upregulation of Ribosome Assembly Factor PNO1 Contributes to Cancer Progression by Negatively Regulating the p53 Signaling Pathway. Cancer research 65 30862720
2021 PNO1 regulates autophagy and apoptosis of hepatocellular carcinoma via the MAPK signaling pathway. Cell death & disease 45 34050137
2020 PNO1, which is negatively regulated by miR-340-5p, promotes lung adenocarcinoma progression through Notch signaling pathway. Oncogenesis 31 32483111
2019 Celecoxib Inhibits Hepatocellular Carcinoma Cell Growth and Migration by Targeting PNO1. Medical science monitor : international medical journal of experimental and clinical research 27 31568401
2003 RRP20, a component of the 90S preribosome, is required for pre-18S rRNA processing in Saccharomyces cerevisiae. Nucleic acids research 22 12736301
2019 Importance of PNO1 for growth and survival of urinary bladder carcinoma: Role in core-regulatory circuitry. Journal of cellular and molecular medicine 20 31800162
2021 MYC-mediated upregulation of PNO1 promotes glioma tumorigenesis by activating THBS1/FAK/Akt signaling. Cell death & disease 19 33664245
2004 Cloning and characterization in Pichia pastoris of PNO1 gene required for phosphomannosylation of N-linked oligosaccharides. Gene 18 14693378
2020 Transcription Factor EBF1 Over-Expression Suppresses Tumor Growth in vivo and in vitro via Modulation of the PNO1/p53 Pathway in Colorectal Cancer. Frontiers in oncology 14 32676457
2004 Cloning and characterization of a novel human RNA binding protein gene PNO1. DNA sequence : the journal of DNA sequencing and mapping 14 15497447
2022 Ribosome assembly factor PNO1 is associated with progression and promotes tumorigenesis in triple‑negative breast cancer. Oncology reports 12 35445733
2022 Circ_0004676 exacerbates triple-negative breast cancer progression through regulation of the miR-377-3p/E2F6/PNO1 axis. Cell biology and toxicology 12 35870038
2012 Pno1 tissue-specific expression and its functions related to the immune responses and proteasome activities. PloS one 11 23029399
2021 Knockdown of PNO1 inhibits esophageal cancer progression. Oncology reports 10 33864661
2023 Inhibition of ribosome assembly factor PNO1 by CRISPR/Cas9 technique suppresses lung adenocarcinoma and Notch pathway: Clinical application. Journal of cellular and molecular medicine 8 36625087
2023 PNO1 promotes the progression of osteosarcoma via TGF-β and YAP/TAZ pathway. Scientific reports 7 38071381
2024 Pien Tze Huang Inhibits Proliferation of Colorectal Cancer Cells through Suppressing PNO1 Expression and Activating p53/p21 Signaling Pathway. Chinese journal of integrative medicine 5 38216838
2025 PNO1 enhances ovarian cancer cell growth, invasion, and stemness via activating the AKT/Wnt/β-catenin pathway. Scientific reports 4 40113869
2024 Clinical significance of PNO1 as a novel biomarker and therapeutic target of hepatocellular carcinoma. Journal of cellular and molecular medicine 4 38722284
2025 PNO1 served as a potential biomarker to promote the stemness and progression of breast cancer via the NF-κB signaling pathway. Stem cells (Dayton, Ohio) 1 40971713
2024 Ribosome Biogenesis and Cancer: Insights into NOB1 and PNO1 Mechanisms. Current pharmaceutical design 1 39143880
2024 miR-326 overexpression inhibits colorectal cancer cell growth and proteasome activity by targeting PNO1: unveiling a novel therapeutic intervention strategy. Scientific reports 1 39414903
2025 The proximity proteome of pre-40S pre-ribosomal particle components PNO1 and NOB1 using turboID proximity labeling technology. Gene 0 40157618

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