Transcription Factors

Extra Levels of Control

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

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

Upstream Promoter Element (UPE)

Transcription Inhibition

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

TATA box binding

Zinc fingers

Zinc Finger II

March 2007 Molecule of the Month by David Goodsell doi: 10.2210/rcsb_pdb/mom_2007_3

http://www.uic.edu/classes/bios/bios100/mike/spring2003/leucinezipper.jpg

Helix-loop-helix

n0b311a.blogspot.com

Helix-turn-helix

FEMS Microbiology Reviews 29 (2005) 231–262