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Gene Regulation in Eukaryotes

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• All cells in an organism contain all the DNA: – all genetic info

Must regulate or control which genes are turned on in which cells

Genes turned on determine cells’ function – E.g.) liver cells express genes for liver enzymes but not genes for stomach enzymes

 

Proteins act in trans DNA sites act only in cis

 

• Trans acting elements (not DNA) can diffuse through cytoplasm and act at target DNA sites on any DNA molecule in cell (usually proteins)

• Cis acting elements (DNA sequences) can only influence expression of adjacent genes on same DNA molecule

 

Eukaryotic Promoters---trans-acting proteins control transcription from class II (RNA pol II) promoters

 

Gene Regulation in Eukaryotes


 

• Basal factors bind to the core promoter – TBP – TATA box binding protein – TAF – TBP associated factors

• RNA polymerase II binds to basal factors

 

Eukaryotic Promoters

 

• Promoter proximal elements are required for high levels of transcription. • They are further upstream from the start site, usually at positions between -50 and -500.

• These elements generally function in either orientation.

• Examples include:

– The CAAT box consensus sequence CCAAT

– The GC box consensus sequence GGGCGG

– Octamer consensus sequence AGCTAAAT