Overview• Transcription is superficially similar to replication, with important
differences.• E. coli RNA polymerase core has an ’ subunit structure.• In Eukaryotes, RNA Pol II transcribes most genes.• Transcription consists of initiation, elongation, and termination.• Initiation occurs at promoters, which are recognized by the subunit and
the -CTD in bacteria.• Promoter strength depends on a close match to the consensus sequence.• Promoter binding is followed by a transition to the open complex.• RNA polymerase transition to elongation phase involves abortive initiation.• Termination is mediated by signals in the RNA.• In Eukaryotes, promoters contain binding sites for TFIID, TF2B, and TBP.• Initiation involves a multiprotein assembly at the promoter.• Elongation is stimulated by elongation factors, and involves the recruitment
of capping, splicing, and polyadenylation proteins.• PolI and PolIII promoters are distinct, but require TBP.
Transcription and RNA Polymerases
RNA Polymerase Structure
Events in Transcription
70 Recognizes Bacterial Promoters
Core polymerase binding is enhanced by sigma and increased temperature.
Promoter Consensus
Polymerase Binding
-CTD contacts the UP element.
-CTD contacts the UP element.
RNA Pol Active Site and Channels
RNA Polymerase melts -9 to +3
The subunit contains the active site.
Termination
Termination
Rho
Three Eukaryotic RNA Polymerases
Eukaryotic Promoter
SV40 Early transcription starts at the same position relative to the TATA box.