BMCB 658 Lecture Notes - Lecture 28: Pribnow Box
Lecture 28: Transcription & RNA Synthesis May 3, 2016
General Features of RNA Synthesis
1. RNA synthesized on a DNA template, catalyzed by DNA-dependent RNA
polymerase
2. ATP, GTP, CTP, and UTP are required, as well as Mg2+
3. No RNA primer is required
4. RNA chain is synthesized in the 5’ to 3’ direction
5. DNA base sequence contains signals for initiation and termination of RNA
synthesis; the polymerase binds to and moves along the DNA template in 3’
to 5’ direction
6. DNA template is unchanged
Transcription Step 1
• DNA template has promoter region upstream to transcription start site,
position +1
• Promoter provides directionality for polymerase
• Tells polymerase which strand is coding strand
• Also controls frequency of gene transcription
• Strong promoter: binds polymerase tightly, gene will be transcribed more
often
Promoter Recognition
• -10 region (Pribnow box)
• -35 region (core promoter)
• -40 to -60 region (UP element) enhanced polymerase binding
Transcription Step 2
• Closed complex is formed
• The sigma subunit directs polymerase to promoter
Transcription Step 3
• Open complex is formed
• The sigma subunit initiates strand separation (melting) ~-10 from TSS
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