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slides-13 - #13 Eukaryotic transcription (III) 1.Type of...

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#13 Eukaryotic transcription (III) 1.Type of transcription activators 2.Structure of transcription activators 3.Mechanisms of transcription activators 4.Regulation of transcription activators 5.Signal transduction
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Prokaryote : Sigma factors δ factor is one of the five subunits of bacterial RNA polymerase. δ factor helps RNA polymerase bind to the promoter. Transcription factors — Bind to DNA to facilitate or inhibit transcription. Eukaryote : General transcription factors —TFII factors are required for the binding of eukaryotic RNA polymerase II, which catalyzes the transcription of all protein-encoding genes, to promoter. Basal transcription complex -- it is a preinitiation complex with only basic protein components (TF factors and RNAP), it has basal (low) level of transcription activity, which can be stimulated by gene specific transcription activators. Gene-specific transcription activators are transcription activators binding to specific DNA sequences of one or more genes. Human genome encode about 2600 (or 10% ) transcription factors, yeast and Arabidopsis each spends ~5% of their genome to encode transcription factors. Transcription factors
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Homeodomain Zinc finger Leucine zipper Helix-loop-helix 1. Types of transcription activators Transcription activators are usually classified by DNA-binding domains Zinc finger : containing C or H, bind zinc ion, monomer ok, (e.g. Sp1, Gal4, GR) Homeodomain : containing homeobox, often also have HLH domain, often regulate organ development (e.g. Ant, Ey, etc) bZIP (basic Leucine Zipper): containing Leu-rich alpha helix DNA-binding domain and basic activation domain, usually act as dimer (e.g. GCN4, Fos, Jun) bHLH (basic helix-loop-helix), containing HLH DNA-binding domain and basic activation domain, usually act as dimer (e.g. Myc, MyoD)
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2. Structure of transcription activators 1. Transcription activators have two major domains: a DNA-binding domain and an activating domain. The DNA-binding domain recognizes specific DNA sequence, activating domain activates transcription. 2. There are at least 4 different types of DNA-binding domains : homeodomain, zinc-finger motif, leucine zipper motif, and helix-loop- helix motif. The DNA-binding domain (or motif) of a transcription factor protein can usually be recognized by the domain-specific amino acid sequence. Activators are usually classified by the DNA-binding domain. 3. There are at least three types of activating domains: acidic domain , basic domain , and Q-rich domain. Activating domains allow transcription factor to interact with other proteins to activate transcription.
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A transcription activator contains a DNA binding domain and a transcription activating domain
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a. Zinc-finger proteins 1. Zinc-finger protein are transcription factors that bind zinc 2+ ions. There are many types of zinc finger proteins with different zinc finger domains. Zinc-finger domains contain regularly spaced cysteines and/or histidines.
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slides-13 - #13 Eukaryotic transcription (III) 1.Type of...

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