1. Transcription Factors
Extra Levels of Control

2. What? Transcription factors (TF) diffusible proteins
act at numerous sites on many chromosomes
Influence transcription by interacting with other proteins or segments of DNA
“Upstream” = being 5’ to the start site
Negative numbers of bases
“Downstream” = being 3’ to the start site
Positive numbers of bases

3. Why? Finer control over transcription
Recruits RNA Polymerase II
Selective expression of specific genes
Protection of promoter sequences
Protection from denaturation & proteolysis
TATA box, upstream promoter element (UPE), Pribnow box, CpG islands, CAAT box, -10 to -35
Adoption of specific 3D conformation of DNA

4. Upstream Promoter Element (UPE)

5. Transcription Inhibition

6. Where? Promoter & enhancer sequences on DNA
On transcriptional elements (TE) or enhansons
In the “open complex” of DNA
In the origin region of DNA
In the helix-loop-helix motif
In leucine zippers
In zinc fingers

7. TATA box binding

8. Zinc fingers

9. Zinc Finger II
March 2007 Molecule of the Month by David Goodsell doi: /rcsb_pdb/mom_2007_3

11. Helix-loop-helix
n0b311a.blogspot.com

12. Helix-turn-helix
FEMS Microbiology Reviews 29 (2005) 231–262