Affinage

POLR1D

DNA-directed RNA polymerases I and III subunit RPAC2 · UniProt P0DPB6

Length
133 aa
Mass
15.2 kDa
Annotated
2026-06-10
13 papers in source corpus 8 papers cited in narrative 8 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

POLR1D is a shared subunit of RNA Polymerases I and III whose principal function is to drive rRNA transcription and ribosome biogenesis, an activity essential for cell proliferation and development (PMID:27448281, PMID:35656583). It heterodimerizes with POLR1C through a dimerization domain, and Treacher Collins syndrome-associated missense mutations (p.Leu55Val, G52E) map to this domain and impair the POLR1D–POLR1C interaction, reducing rRNA production (PMID:24603435, PMID:35656583). Loss of POLR1D function depletes ribosome biogenesis and triggers Tp53-dependent neuroepithelial apoptosis, producing the neural crest cell deficiency that underlies craniofacial malformation (PMID:27448281). The requirement for POLR1D is cell-autonomous and absolute in early mammalian development: knockout mouse embryos accumulate DNA damage, fail trophectoderm specification, and arrest before blastocyst formation (PMID:33022126). Beyond its nuclear transcriptional role, a cytoplasmic pool of POLR1D interacts with the mTORC1 regulators RAGA and RAPTOR, enhancing their association and sustaining mTORC1 activity, including under starvation (PMID:40222657). In cancer, amplification and overexpression of POLR1D upregulates VEGFA, promotes proliferation, and emerges as an acquired bevacizumab-resistance mechanism in colorectal cells (PMID:32087735).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2014 Medium

    Established POLR1D as a Treacher Collins syndrome gene and localized the causative lesion to its dimerization domain, implicating polymerase assembly in craniofacial disease.

    Evidence Direct sequencing in consanguineous families plus RT-PCR of TCOF1 mRNA

    PMID:24603435

    Open questions at the time
    • Dimerization defect inferred from domain location, not measured biochemically
    • Mechanistic link between POLR1D mutation and reduced TCOF1 mRNA not established
  2. 2016 High

    Placed POLR1D upstream of Tp53-dependent apoptosis, explaining how a ribosome biogenesis defect translates into neural crest deficiency and skeletal anomalies.

    Evidence Zebrafish polr1c/polr1d mutants with genetic epistasis (tp53 inhibition rescue) and rRNA transcription assays

    PMID:27448281

    Open questions at the time
    • Does not define how reduced rRNA specifically activates Tp53 in neuroepithelium
    • Tissue selectivity of the neural crest phenotype unexplained
  3. 2020 High

    Demonstrated that POLR1D is essential and cell-autonomous in the earliest mammalian development, linking its loss to DNA damage and failed lineage specification.

    Evidence Polr1d knockout mouse embryo recovery, culture, DNA damage and trophectoderm specification analysis

    PMID:33022126

    Open questions at the time
    • Mechanism connecting POLR1D loss to DNA damage not resolved
    • Whether the phenotype is purely Pol I/III transcription-dependent untested
  4. 2020 Medium

    Revealed an oncogenic role: POLR1D amplification upregulates VEGFA and confers acquired resistance to anti-angiogenic therapy, distinct from its developmental function.

    Evidence cfDNA whole-genome sequencing of patients plus in vitro POLR1D overexpression with expression and viability assays

    PMID:32087735

    Open questions at the time
    • Mechanism by which POLR1D upregulates VEGFA not defined
    • Single lab; causality of resistance in vivo not established
  5. 2022 High

    Provided direct biochemical proof that a TCS mutation impairs POLR1D–POLR1C heterodimerization, connecting dimerization loss to reduced rRNA and developmental arrest.

    Evidence In vitro heterodimerization assay with mutagenesis and Drosophila mutant rRNA/growth analysis

    PMID:35656583

    Open questions at the time
    • Structural basis of the dimerization interface not resolved
    • Quantitative link between residual dimerization and disease severity unaddressed
  6. 2024 Low

    Implicated POLR1D in lung cancer cell proliferation, migration, and invasion via PI3K-Akt signaling.

    Evidence RNAi knockdown in two lung cancer cell lines with viability, transwell, and Western blot pathway readouts

    PMID:38844975

    Open questions at the time
    • No direct mechanistic link between POLR1D and PI3K-Akt established
    • Single knockdown approach, single lab, no rescue
  7. 2025 Medium

    Identified a moonlighting cytoplasmic function: POLR1D binds RAGA and RAPTOR to enhance their interaction and sustain mTORC1 signaling, extending its role beyond nuclear transcription.

    Evidence Overexpression/knockdown with mTORC1 activity assays, reciprocal Co-IP, and subcellular fractionation in human cells

    PMID:40222657

    Open questions at the time
    • Single lab; in vivo relevance of cytoplasmic POLR1D pool untested
    • How POLR1D partitions between nuclear polymerase and cytoplasmic mTORC1 roles unknown
  8. 2025 Medium

    Connected POLR1D to tissue-specific endocrine control by showing prothoracic gland knockdown disrupts ecdysone signaling through impaired ribosome and Pol III 7SK RNA synthesis.

    Evidence Tissue-specific Drosophila RNAi with ecdysone rescue, nucleolar imaging, and ribosome/7SK RNA measurements

    PMID:40317818

    Open questions at the time
    • Generalizability beyond Drosophila prothoracic gland unknown
    • Relative contributions of Pol I versus Pol III deficits not separated

Open questions

Synthesis pass · forward-looking unresolved questions
  • How POLR1D balances its core Pol I/III transcription role against its cytoplasmic mTORC1 and oncogenic VEGFA functions, and what governs its subcellular partitioning, remains unresolved.
  • No structural model of the POLR1D–POLR1C interface in the polymerase context
  • Mechanism coupling rRNA depletion to Tp53 and DNA damage undefined
  • Cytoplasmic mTORC1 function not validated in vivo

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140098 catalytic activity, acting on RNA 3 GO:0060089 molecular transducer activity 1
Localization
GO:0005730 nucleolus 1 GO:0005829 cytosol 1
Pathway
R-HSA-1266738 Developmental Biology 2 R-HSA-74160 Gene expression (Transcription) 2 R-HSA-162582 Signal Transduction 1
Partners
POLR1CRPTORRRAGA
Complex memberships
RNA Polymerase IRNA Polymerase III

Evidence

Reading pass · 8 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2016 Loss-of-function of polr1c and polr1d in zebrafish results in deficient ribosome biogenesis, Tp53-dependent neuroepithelial cell death, and a deficiency of migrating neural crest cells; genetic inhibition of tp53 suppresses neuroepithelial cell death and ameliorates skeletal anomalies, placing polr1d upstream of Tp53-dependent apoptosis in craniofacial development. Zebrafish homozygous mutant analysis, genetic epistasis (tp53 inhibition suppresses polr1d mutant phenotype), rRNA transcription assays PLoS genetics High 27448281
2014 A homozygous missense mutation in POLR1D (p.Leu55Val) localised in the dimerization domain of the RNA polymerase subunit causes Treacher Collins syndrome with autosomal recessive inheritance, and is associated with a ~50% reduction in TCOF1 mRNA levels. Direct sequencing of POLR1D in consanguineous families; functional analysis by real-time quantitative RT-PCR for TCOF1 mRNA levels Genetics in medicine Medium 24603435
2022 A TCS-associated missense mutation G52E in human POLR1D (and the equivalent G30R/G30E in Drosophila) reduces the ability of POLR1D to heterodimerize with POLR1C in vitro; in Drosophila, the G30R mutation reduces larval rRNA levels, slows larval growth, and arrests larval development, and POLR1D is required for development of neural and non-neural cells. In vitro heterodimerization assay (POLR1D with POLR1C), Drosophila mutant analysis, rRNA level measurements, RNAi knockdown screen Developmental dynamics High 35656583
2020 Polr1d homozygous knockout mouse embryos fail to develop beyond the morula stage, cannot form blastocysts, and exhibit severe DNA damage; trophectoderm specification is compromised in the absence of Polr1d, demonstrating an essential cell-autonomous role in early mammalian embryogenesis. Mouse knockout, embryo recovery and culture at E3.5 and E7.5, DNA damage analysis, lineage specification assessment Molecular reproduction and development High 33022126
2020 Amplification and overexpression of POLR1D on chromosome 13q12.2 in colorectal cancer cells upregulates VEGFA expression and promotes cell proliferation, and this amplicon emerges under bevacizumab treatment, constituting an acquired resistance mechanism. Whole-genome sequencing of plasma cell-free DNA, in vitro cell model with POLR1D overexpression, gene expression assays, cell viability assays Genome medicine Medium 32087735
2025 POLR1D overproduction in human cells stimulates mTORC1 activity, while POLR1D downregulation represses the mTORC1 pathway; a cytoplasmic pool of POLR1D interacts with the mTORC1 regulators RAGA and RAPTOR, enhances the RAPTOR-RAGA interaction, and sustains mTORC1 activity under starvation conditions. Overexpression and knockdown in human cells, mTORC1 activity assays, co-immunoprecipitation of POLR1D with RAGA and RAPTOR, subcellular fractionation (cytoplasmic localization) Biochimica et biophysica acta. Molecular cell research Medium 40222657
2024 Silencing POLR1D in lung cancer cell lines inhibits cell proliferation, migration, and invasion, and suppresses activation of the PI3K-Akt signaling pathway as assessed by Western blotting of pathway components. POLR1D RNAi knockdown in SK-MES-1 and H2170 lung cancer cells; CCK-8 viability assay, transwell migration/invasion assay, Western blot for PI3K-Akt pathway proteins Journal of cardiothoracic surgery Low 38844975
2025 Polr1D RNAi knockdown in the Drosophila prothoracic gland causes larval developmental arrest due to defective peripheral ecdysone signaling, impairs prothoracic gland cell growth and nucleolar structure, reduces mature ribosome synthesis, and decreases Pol III-transcribed 7SK RNA production; developmental arrest is partially rescued by exogenous ecdysone treatment. Tissue-specific RNAi knockdown in Drosophila prothoracic gland, ecdysone rescue assay, nucleolar structure imaging, ribosome and 7SK RNA level measurements Developmental dynamics Medium 40317818

Source papers

Stage 0 corpus · 13 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2016 The Roles of RNA Polymerase I and III Subunits Polr1c and Polr1d in Craniofacial Development and in Zebrafish Models of Treacher Collins Syndrome. PLoS genetics 88 27448281
2014 Autosomal recessive POLR1D mutation with decrease of TCOF1 mRNA is responsible for Treacher Collins syndrome. Genetics in medicine : official journal of the American College of Medical Genetics 54 24603435
2020 Cell-free DNA analysis reveals POLR1D-mediated resistance to bevacizumab in colorectal cancer. Genome medicine 35 32087735
2020 Loss of POLR1D results in embryonic lethality prior to blastocyst formation in mice. Molecular reproduction and development 9 33022126
2019 Expression and Clinical Significance of POLR1D in Colorectal Cancer. Oncology 6 31722331
2022 A clinically-relevant residue of POLR1D is required for Drosophila development. Developmental dynamics : an official publication of the American Association of Anatomists 5 35656583
2022 Intrafamilial Phenotypic Heterogeneity in a Chinese Family with a POLR1D p.Q31Rfs*10 Variant: A Challenge in Prenatal Diagnosis. Molecular syndromology 3 36158048
2025 POLR1D, a shared subunit of RNA polymerase I and III, modulates mTORC1 activity. Biochimica et biophysica acta. Molecular cell research 2 40222657
2025 Tissue-specific requirement of Polr1D in the prothoracic gland for ecdysone-mediated developmental transitions in Drosophila melanogaster. Developmental dynamics : an official publication of the American Association of Anatomists 1 40317818
2024 POLR1D silencing suppresses lung cancer cells proliferation and migration via inhibition of PI3K-Akt pathway. Journal of cardiothoracic surgery 1 38844975
2025 Maternal antioxidant treatment partially rescues developmental defects in a Drosophila Polr1D mutant model. microPublication biology 0 40583963
2025 A POLR1D-regulating single-nucleotide polymorphism as a predictive marker candidate for platinum-based chemotherapy in gastrointestinal cancers. Therapeutic advances in medical oncology 0 40661991
2025 A novel pathogenic variant in POLR1D (c.220dup, p.His74ProfsTer8) causes Treacher Collins syndrome type 2 in a Chinese patient: a case report. BMC pediatrics 0 41455926

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