lec.8-10. euk_trxn_control

lec.8-10. euk_trxn_control - Eukaryotic transcriptional...

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Eukaryotic transcriptional control: major considerations 1. Interplay among multiple general transcription factors; activators/repressors; mediator/coactivators 2. Multiple regulatory sequences: proximal and distant 3. Chromatin and its impact on transcription 1. Co-transcriptional RNA processing 1. Regulation of transcriptional regulators
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Sequence-specific transcription factors are modular Modular structure of Sp1
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Experiments to map the DNA- binding and activation domain of yeast GAL4 protein
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DNA-binding domains can be classified into many structural types
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One type of zinc finger protein (C2H2) This protein belongs to the Cys-Cys-His-His family of zinc finger proteins, named after the amino  acids that grasp the zinc. This zinc finger is from a frog protein of unknown function. (A)  Schematic drawing of the amino acid sequence of the zinc finger. (B) The three-dimensional  structure of the zinc finger is constructed from an antiparallel β  sheet (amino acids 1 to 10)  followed by an α  helix (amino acids 12 to 24). The four amino acids that bind the zinc (Cys 3,  Cys 6, His 19, and His 23) hold one end of the α  helix firmly to one end of the  β  sheet. (Adapted  from M.S. Lee et al.,  Science  245:635-637, 1989. © 1989 the AAAS.)
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The binding of transcription factors to the major groove of DNA As with most bacterial activators and repressors, α helices in the DNA-binding domain of eukaryotic transcription factors are often oriented so that they lie in the major groove of DNA helix where atoms of protein and DNA make contact through specific H-bonds and van der Waals interactions. Typically, a protein-DNA interface consists of 10 to 20 such contacts, involving different amino acids, each contributing to the binding energy of the protein-DNA interaction.
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DNA binding by a zinc finger protein   (A) The structure of a fragment of a mouse gene regulatory protein bound to a specific DNA site. This  protein recognizes DNA using three zinc fingers of the Cys-Cys-His-His type arranged as direct repeats.  (B) The three fingers have similar amino acid sequences and contact the DNA in similar ways. In both (A)  and (B) the zinc atom in each finger is represented by a small sphere. (Adapted from N. Pavletich and C.  Pabo,  Science 252:810-817, 1991. © 1991 the AAAS.)
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The basic helix-loop- helix protein Max binds DNA as a dimer
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Leucine zipper (aka b-Zip) proteins (e.g. Fos, Jun, & yeast GCN4) bind DNA as dimers Leu residues at every seventh position down one side of the α -helix. Two α -helical monomers form a coiled-coil dimer. Basic amino acid residues N-terminal to the leucine zipper form the DNA-binding domain.
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Heterodimeric transcription factors increase regulatory diversity and gene-control options (a) Many transcription factors (e.g. b-Zip
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This note was uploaded on 03/08/2010 for the course MCB 110 taught by Professor Alber,zhou,nogales during the Fall '07 term at Berkeley.

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lec.8-10. euk_trxn_control - Eukaryotic transcriptional...

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