lecture 6_Prokaryotic Transcription

Transcription

the process of copying (transcribing) RNA from DNA

Promoter

regions of DNA where transcription starts

Promoter elements

DNA sequences (TATAAT, TTGACAT) where
RNA polymerase holoenzyme complex binds and starts transcription

+1

transcription start site

-1

promoter start site

UTR

untranslated region sequence (5' and 3')

Transcription in bacteria is mediated
by

RNA polymerase holoenzyme complex

Composed of a core enzyme

RNA polymerase and a co-factor called
Sigma factor (protein)

There is only one RNA polymerase

in bacteria

Organisms use sigma factors as

a switch to regulate gene expression (ON or OFF)

Sigma protein

Initiates transcription by binding to the promoter sequences and recruits RNA polymerase

RNA polymerase protein

Unwinds DNA and adds
nucleotides

Rudder protein

Steers the DNA inside the RNA polymerase enzyme

Zipper protein

Separates RNA from DNA

Nucleotide termination signal

40 bp GC-rich inverted repeats
followed by 6 or more adenine nucleotides.

RNA hairpin
stem loop

transcribed which disrupts the interaction between RNA polymerase and RNA