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Chapter 18, 19: Regulation of Gene Expression A - Coggle Diagram

- - - - transcription
      - translation
      - degradation of mRNA or protein
    - - protein cleavage
      - protein modifications (phosphorylation, glycosylation, methylation, acetylation, etc.)
- - - - In bacteria, functionally-related proteins are often produced from a single transcript, produced by an operon
        
        --> independent translation into separate peptides
        
        ex. transcription of enzymes involved in tryptophan biosynthesis is repressed by tryptophan (transcriptional repression)
        
        the trp operon is a repressible operon (repressor is only active when bound by tryptophan)
        
        Allosteric regulation of trpR by tryptophan promotes DNA binding
        
        the lac operon is an inducible operon
        
        lac operon is repressed in absence of lactose
        
        when lactose (inducer) binds to lac repressor --> prevents the lac operon from binding to the operator so it inactivates lac operon's repression --> operon can now be transcribed
    - - transcription of eukaryotic genes is regulated by proteins that bind to enhancers located in and around genes
        
        What's an enhancer?
        
        cis-acting DNA sequence that can elevate levels of transcription from an adjacent promoter
        
        enhancers are bound by proteins (regulatory transcription factors) that promote transcription. Different transcription factors (enhancer-binding proteins) bind different enhancer sequences
        
        location: may be very distance from the promoter - upstream, downstream, even within introns
        
        procedure for enhancer
        
        enhancer binding proteins interact with mediator proteins --> that interact with general transcription factors --> create transcription inintiation complex --> RNA polymerase can bind in promoter --> RNA synthesis
- - - - Regulation by red/far red light
        
        red light: gene is turned on
        
        red light/far red light: turn off gene
        
        red/far/red: turn on gene
        
        dark: no RNA
      - Regulation by circadian clock: begins to be transcribed before daylight (anticipates daylight)
      - Red-light induction AND circadian transcription pattern of LHCB is regulated by enhancer binding protein, CCA1
        
        high levels of CCA1 protein binds to enhancer --> appearance of LHCB --> promotes transcription
- - - - albumin gene is turned ON, crystalline gene is turned OFF
  - - - the genes that are present in particular cells depend on the specific transcription factors that bind to the enhancers in the cell
        
        how it's expressed depends on the combo of transcription factors: i.e. binds 3/4 enhancers --> gene expression is HIGH, binds 1/4 of enhancers --> gene expression is LOW
        
        different cells have different combinatorial control of transcription
- - - - myoD regulates transcription of other gene that's also a transcription factor which regulates the transcription of other genes
        
        differentiated cell