RNA polymerase

Definition

An enzyme complex that catalyzes DNA-directed RNA synthesis (transcription), producing messenger RNA, ribosomal RNA, or transfer RNA from a DNA template. In eukaryotes including insects and arachnids, distinct polymerases handle different RNA classes: RNA polymerase I synthesizes most rRNA, RNA polymerase II produces mRNA and some regulatory RNAs, and RNA polymerase III makes tRNA and small RNAs. The enzyme's activity is regulated by transcription factors, hormones, and environmental cues that coordinate development, metamorphosis, and stress responses in arthropods.

Etymology

RNA (ribonucleic acid) + polymerase (enzyme that polymerizes), from Greek polys 'many' + meros 'part'

Example

In the silkworm Bombyx mori, RNA polymerase II activity increases dramatically during the larval-pupal transition as ecdysone triggers widespread transcriptional reprogramming; inhibitors of this enzyme, such as alpha-amanitin, block molting and can be lethal.

Synonyms

• DNA-dependent RNA polymerase
• DdRP
• transcriptase

Related Terms

• Transcription
• promoter
• ecdysone receptor
• Gene expression
• RNA interference
• Nucleolus
• polymerase chain reaction

Usage Notes

Distinguish RNA polymerase (uses DNA template) from RNA-dependent RNA polymerases found in some viruses and used in laboratory RNA amplification. In arthropod studies, RNA polymerase II is frequently assayed as a marker of transcriptional activity during development or in response to xenobiotics. The enzyme is a target of several natural toxins (amanitins, tagetitoxin) and some antiviral strategies that exploit arthropod RNA polymerase machinery.