ABSTRACT
Key Notes
In eukaryotes, RNA is synthesized by three RNA polymerases: RNA Pol I is a nucleolar enzyme that transcribes rRNAs, RNA Pol II is located in the nucleoplasm and transcribes mRNAs and most snRNAs, RNA Pol III is also nucleoplasmic and transcribes tRNA and 5S rRNA, as well as U6 snRNA and the 7S RNA of the signal recognition particle (SRP).
Each RNA polymerase transcribes only one strand, the antisense (−) strand, of a double-stranded DNA template, directed by a promoter. Synthesis occurs 5′ → 3′ and does not require a primer.
Each of the three RNA polymerases contains 12 or more subunits, some of which are similar to those of E. coli RNA polymerase. However, four to seven subunits in each enzyme are unique to that enzyme.
Related topics
DNA structure (F1)
RNA structure (G1)
Transcription in prokaryotes (G2)
The lac operon (G3)
The trp operon (G4)
Transcription of protein-coding genes in eukaryotes (G6)
Regulation of transcription by RNA Pol II (G7)
Processing of eukaryotic pre-mRNA (G8)
Ribosomal RNA (G9)
Transfer RNA (G10)
