Question

Describe briefly the structure and subunits of prokaryotic and eukaryotic RNA polymerases. Describe in detail at least three ways that prokaryotic and eukaryotic transcription differ from each other.

Answer 1

• A comparative overview of the subunit taxonomy and sequence of eukaryotic and prokaryotic RNA polymerases indicates the presence of a core structure conserved between both sets of enzymes.

The difference between them is ascribed to domains and subunits peripheral to the largely conserved Central structure.possible subunits and domain functions are outlined.The cores flexible shape is largely determined by the elongated architecture of the two largest subunits,which can be oriented along the DNA axis with the bulkier amino-terminal head regions looking towards the 3' end of the gene to be transcribed and their more slender carboxyl terminal domains at the tail of the enzyme.The two largest prokaryotic subunits appear originally derived from a single gene.

• Difference between them :

1) Prokaryotes only contain 3 different promoter elements:- 10,-35promoters and upstream elements.

2)Another main difference between them is that transcription and translation occurs simultaneously in prokaryotes and in eukaryotes the RNA transcribed in the nucleus and then translated in the cytoplasm.

3)RNAfrom eukaryotes undergo post transcriptional modifications events including capping, splicing etc...These events do not occur in prokaryotes.