lec 11.1 - eukaryotic transcription regulation (copy)

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RECALL: levels of transcription control in prokaryotes

  1. Transcription initiation

  2. Post-transcriptional processes

  3. RNA stability

  4. Translation

  5. Protein modification

  6. Protein transport

  7. Protein degradation

<ol><li><p>Transcription initiation</p></li><li><p>Post-transcriptional processes</p></li><li><p>RNA stability </p></li><li><p>Translation</p></li><li><p>Protein modification </p></li><li><p>Protein transport</p></li><li><p>Protein degradation</p></li></ol>
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when is gene expression principally controlled?

at the initiation of transcription

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what is an additional control level found in eukaryotes?

  • Activation of gene structure: epigenetics to open/close chromatin

  • Chromatin structure can persist through cell division, called the epigenetic state

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how are genes turned on?

  • first mechanism

  • first mechanism: When replication disrupts chromatin structure, after the Y fork has passed, either chromatin can reform or transcription factors can bind and prevent chromatin formation

  • transcription factors bind promoters to keep open access to the genes and prevent nucleosomes from reforming

<ul><li><p>first mechanism: When replication disrupts chromatin structure, after the Y fork has passed, either chromatin can reform or transcription factors can bind and prevent chromatin formation</p></li></ul><p></p><ul><li><p>transcription factors bind promoters to keep open access to the genes and prevent nucleosomes from reforming</p></li></ul>
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how are genes turned on?

  • second mechanism (briefly describe)

  • second mechanism: transcription factors can bind to DNA on outside of histones and recruit histone modifiers to go open up gene region: either uni or bi directionally until it reaches an insulator (Boundary element)

<ul><li><p>second mechanism: transcription factors can bind to DNA on outside of histones and recruit histone modifiers to go open up gene region: either uni or bi directionally until it reaches an insulator (Boundary element)</p></li></ul>
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what are the components of the second mechanism?

  • TAF – transcription activating factors

  • TBP – TATA binding factor

  • TF - transcriptional factor - activated by a cell or env’t signal and recruits the CBP-PCAF-HAT complex which binds to the SWI/SNF complex which is an ATP- dependent chromatin remodeling complex and brings RNA polymerase to region to start transcription

    • HAT complex: histone acetyl transferase transfers acetyl groups onto histones to hide their positive charge (makes them less attracted to DNA which is negative)

    • SWI/SNF: moves histones to get better access

<ul><li><p><strong>TAF </strong>– transcription activating factors</p></li><li><p><strong>TBP </strong>– TATA binding factor</p></li><li><p><strong>TF </strong>- transcriptional factor - activated by a cell or env’t signal and recruits the <strong>CBP-PCAF-HAT</strong> complex which binds to the <strong>SWI/SNF</strong> complex which is an ATP- dependent chromatin remodeling complex and brings RNA polymerase to region to start transcription</p><ul><li><p><strong>HAT complex: </strong>histone acetyl transferase transfers acetyl groups onto histones to hide their positive charge (makes them less attracted to DNA which is negative)</p></li><li><p><strong>SWI/SNF</strong>: moves histones to get better access</p></li></ul></li></ul>
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activator

a molecule that determines the frequency of
transcription – usually upregulation

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repressor

A protein that inhibits expression of a gene.

  • It may act to prevent transcription by binding to a regulator site (e.g. promoter to block access) in DNA or by preventing translation by binding to RNA.

  • downregulation

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positive control

  • The default state of genes that are under positive control is that they cannot be expressed unless a positive regulator is bound

  • need inducer

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true activator

A positive transcription factor that functions by
making contact, direct or indirect, with the basal apparatus to activate transcription.

  • binds to DNA and activates RNA pol

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