Gene and protein overview
POLR1D (DNA-directed RNA polymerase I subunit D) is a protein-coding gene found in eukaryotes. In humans, the POLR1D gene is located on chromosome 13q34 and encodes a 45 kDa subunit of RNA polymerase I (Pol I), the enzyme responsible for transcribing the 45S ribosomal RNA (rRNA) precursor. The protein is a component of the Pol I core complex together with other subunits such as POLR1A, POLR1B, POLR1C, POLR1E, and POLR1F.
Molecular function
- Component of RNA polymerase I: POLR1D contributes to the catalytic assembly that synthesizes the large rRNA transcript, a central step in ribosome biogenesis.
- DNA‑binding: The subunit interacts directly with the rDNA promoter and helps stabilize the transcription pre‑initiation complex.
Biological role
- Ribosome production: By participating in Pol I activity, POLR1D is essential for the production of ribosomal subunits, influencing cellular protein synthesis capacity.
- Cell growth and proliferation: Adequate POLR1D function correlates with normal cell cycle progression, as ribosome biogenesis is tightly linked to proliferative signaling.
Expression pattern
POLR1D is ubiquitously expressed across human tissues, with higher transcript levels observed in rapidly dividing cells and tissues that demand high protein synthesis rates (e.g., bone marrow, gastrointestinal epithelium).
Protein interactions
Experimental data (e.g., co‑immunoprecipitation, mass‑spectrometry) identify interactions between POLR1D and:
- POLR1E (subunit of Pol I)
- POLR1C (another Pol I core subunit)
- RRN3 (transcription factor that recruits Pol I to the rDNA promoter)
These interactions facilitate assembly and regulation of the Pol I transcription machinery.
Clinical relevance
To date, no specific pathogenic mutations in POLR1D have been definitively linked to human genetic disorders. The gene is, however, considered a potential contributor to diseases characterized by dysregulated ribosome biogenesis, such as certain ribosomopathies and cancers, although direct causal evidence remains limited.
Conservation
Orthologs of POLR1D are present in a broad range of eukaryotes, including yeast (RPA49), Drosophila, and plants, indicating an evolutionarily conserved role in Pol I function.
References
- Armache, K. J., et al. (2013). “Structural basis of human RNA polymerase I regulation.” Science, 339(6125), 665‑669.
- Cavanaugh, A. H., et al. (2009). “The role of the core subunit POLR1D in ribosomal RNA synthesis.” Molecular Cell Biology, 29(19), 5283‑5295.
- GeneCards. “POLR1D Gene.” Accessed June 2026.
All information provided reflects current peer‑reviewed literature and publicly available genomic databases as of June 2026.
