RNA Polymerases

RNA polymerases catalyze genome transcription, converting genetic information into RNA outputs that support gene expression, ribosome biogenesis, protein synthesis, and cell growth^[1]. In eukaryotic cells, three nuclear enzymes divide this work: RNA polymerase I (Pol I) transcribes ribosomal DNA, RNA polymerase II (Pol II) produces mRNAs and many regulatory non-coding RNAs, and RNA polymerase III (Pol III) generates tRNAs, 5S rRNA, and other short non-coding RNAs^[2][3]. Mechanistically, Pol I and Pol III support ribosome production and translation capacity, whereas Pol II links transcription initiation, elongation, RNA processing, and gene-specific regulation through its C-terminal domain^[4]. In disease models, disruption of Pol I or Pol III function produces tissue-specific developmental disorders, especially craniofacial abnormalities and leukodystrophy or neurodegenerative phenotypes^[3]. Compared with Pol II, Pol I and Pol III are distinguished by high-output non-coding RNA transcription and by specialized subunits that define isoform-specific transcription programs^[2][3]. For experimental applications, Pol I inhibition with CX-5461 suppresses rDNA transcription and has been used to study p53 activation, nucleolar stress, DNA damage response, and cancer cell vulnerability^[5][6]. Pol III inhibition also provides aging-model utility, because reduced Pol III activity extends lifespan in yeast, worms, and flies downstream of TORC1^[7].