1Cademy - Eukaryotic RNA Transcription (Initiation)

Concept

Eukaryotic RNA Transcription (Initiation)

RNA transcription in eukaryotes differs from prokaryotes in that it has many RNA polymerases and it has a more complex control sequence.
Numbers of RNA Polymerases:
- RNA polymerase 1 – synthesizes the precursor to mRNA
- RNAP II – synthesizes mRNA precursors
- RNAP III- synthesizes precursors to 5S rRNA (subunit of ribosome), tRNA, and smaller RNAs.
- Mitochondrial and chloroplasts RNA polymerases are also present .
These all recognize different promoters as well. However core promoters are the TATA box that is present 25-31 base pairs upstream of the transcription start site.
Enhancers – are recognized by transcription factors that attract RNA polymerase II to bind to a nearby promoter. These are important in selective gene expression.
Transcription factors initiation transcription by binding specifically to the promoters of DNA. This is a same process in eukaryotes and prokaryotes.
At the TATA box a preinitaiton complex forms with the RNA polymerase transcription factors and the DNA promoter region.
The TATA binding protein binds to the TATA box. It forms a TFIID complex with 17 other proteins.