Chem 40 Reviewer

11.5 Transcription Regulation in Eukaryotes

Basal level
- Low level of transcription

Activators
- Gene specific transcription factors

Enhancers
- Regulatory sequences that augment transcription

Silencers
- Regulatory sequences that diminish transcription

Initiator
- RNA polymerase II
- Promoter, together with TATA (TFIID)

*Looping enhances transcription

Transcription-coupled Repair (TCR)
- DNA repair mechanism

Response Elements
- Enhancers that respond to metabolic factors
- Ex. Heat-shock element (HSE), glucocorticoid-response element (GRE), metal-response element (MRE), and cyclic-AMP-response element (CRE)

Heat-shock Response Element
- Elevated temperatures lead to the production of heat-shock transcription factors that activate the associated gene
- Physiological signal: heat-shock
- Consensus Sequence: CNNGAANNTCCNNG, where N stands for any nucleotide
- Transcription Factor: HSTF
- Size: 93 kDa

Glucocorticoid-Response Elements
- Glucocorticoid hormone binds to a steroid receptor, this becomes a transcription factor that will bind to GRE
- Physiological Signal: Presence of glucocorticoids
- Consensus Sequence: TGGTACAAATGTTCT
- Transcription Factor: Glucocorticoid receptor
- Size: 94

Cyclic-AMP-Response Element
- Physiological Signal: cAMP-dependent activation of protein kinase A
- Consensus Sequence: TGACGTCA
- Transcription Factors: CREB, CREM, ATF1
- Size: 43

Metal-Response Element
- Physiological Signal: Presence of Cadmium
- Consensus Sequence: CGNCCCGGNCNC

cAMP
- Involved in the control of prokaryotic operons via CAP proteins
- When levels of cAMP rise, activity of cAMP-dependent protein kinase (Protein Kinase A) is stimulated

Cyclic-AMP
- Produced as a second messenger from several hormones (e.g. epinephrine and glucagon)

Protein Kinase A
- Phosphorylates many other proteins and enzymes inside the cell
- Usually associated with switching cell to a catabolic mode
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