eukaryotic transcription

Whats the general overview of the process of transcription in eukaryotes?

• Overall, highly similar to transcription in prokaryotes

• Key differences in enzymes, transcription factors, and post- transcriptional processing used

• dsDNA needs to disassociate

• RNA polymerase recognize start site

• Synthesis of transcripts

• Multiple different RNA Pols

• Transcription in nucleus

• Translation in cytoplasm

Whatre the important proteins of eukaryotic transcription and what do they do?

• RNA Polymerase I – Resides in nucleolus and synthesizes the large ribosomal precursor, 70-80% of RNA generated comes from pol 1 

• RNA Polymerase II – Resides in nucleus and synthesizes mRNA, snoRNA, snRNA, and microRNAs

• RNA Polymerase III – Resides in nucleus and synthesizes tRNA, 5S rRNA and some snRNA

• Transcription factors – Molecules responsible for interpreting promoters and controlling transcription initiation

Whatre the 2 parts of RNA pol 2 and what do they do?

• Holoenzyme
  • Contains 12 subunits
  • DNA duplex leaving enzyme at ~ 90° angle to incoming DNA duplex

• Catalytic core
  • Consists of 10 subunits
  • Catalytically active but requires RPB4/RPB7 complex and general transcription factors to start transcription

Explain the open reading frame in eukaryotes as opposed to prokaryotes

• Like prokaryotes they have 5’ UTR and 3’ UTR, difference is in between start and stop codon, eukaryotes have introns which wont be transcribed and in mature RNA

• Eukaryotes have pre-mRNA and poly-A tail

• Eukaryotes also have enhancer/ silencer sequences sometimes which are very promiscuous sequences and are cis genes regulating the entire process

• 2 pieces in the promoter in eukaryotes which are proximal and core