lec 11.1 - eukaryotic transcription regulation

list the 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

when is gene expression principally controlled?

at the initiation of transcription

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

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

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 go open up gene region: either uni or bi directionally until it reaches an insulator (Boundary element)

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

activator

a molecule that determines the frequency of
transcription – usually upregulation

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

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

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