Please enable JavaScript.

Coggle requires JavaScript to display documents.

Chapter 22- Translation, Chapter 26 - Eukaryotic Gene Regulation,…

- - - - The order:
        
        30S with IF-3 binds to mRNA (50S cannot bind)
        
        IF-3 is released to allow 50S binding.
    - - IF2 and fmet tRNA
        
        fmet tRNA is recognized by IF2. Efficiency of translation initiation increases. IF2 transfer fmet tRNA into P site.
        
        fmet-tRNA prevents elongation because aa.s in the end of the all tRNAs are paired except fmet-tRNA
        
        3GC in the stem of the fmet-tRNA provide entry to P site.
        
        Only aa-tRNA enters A site of 70S ribosome.
        
        The order:
        
        30S- mRNA complex
        
        IF2-GTP joins complex
        3.
        Initiator tRNA joins
        
        IF 1-3 are released then 50S binds. (GDP- Pi form)
  - - - Kirromycin
        – An antibiotic that inhibits protein synthesis by acting on EF-Tu.
    - - Puromycin
        An antibiotic that terminates protein synthesis by mimicking a tRNA and becoming linked to the nascent protein chain.
    - - In the presence of fusidic acid,
        one round of translocation occurs; EF-G binds to the ribosome, GTP is hydrolyzed, and the ribosome moves over by three nucleotides
- - - - IRES
        
        40S subunit associates directly with an internal ribosome entry site (IRES).
        
        Any AUG codons that may be in the 5′ UTR are bypassed entirely
        
        Important in picornavirus infection that destroys cap and inhibition factors.
    - - Initiator tRNA
        is Met-tRNA ( modifications are different. Different secondary or tertiary structure.) Instead of formylation there is phosphorylation at 2' carbon in the ribose.
        
        Met-tRNAi : used for initiation
        
        Met-tRNAm : used in elongation
        
        eIF2 is also rate limiting factor. GTP active form. Forms tertiary complex that critical for the assembly of the ribosome.
        
        eIF2 hydrolyzes its GTP to enable its release together with IF3.
        
        The subunit (alfa) eIF2 is a target for regulation.
        
        eIF4F: heterotrimer contains
        
        G: scaffold protein binds to poly a tail binding protein ( PABP)
        
        E: interacts with 5'cap regulated by phosphorylation via kinases. Kinases can modify this initiation factors. (like stress)
        
        A: helicase, unwinds the 5' structure that allows ribosome to go smoothly
        
        B: mediates 60S join
        
        Poly A-tail stimulates cap-binding complex.
        
        eIF1 and eIF1A help the 43S initiation complex to “scan” the mRNA until it reaches an AUG codon.
        
        eIF5B mediates joining of the 60S and 40S subunits.
        
        Joining of the 60S subunit with the initiation complex cannot occur
        until eIF2 and eIF3 have been released from the initiation complex.
        This is mediated by eIF5 and causes eIF2 to hydrolyze its GTP.
        
        Forming an intact ribosome that is ready to start
        elongation
- - - - Architectural proteins
      - Antirepressors
      - True activators
    - - Activators must have functions
      - The wto hybrid assay detects protein
      - Activators interact with basal aparatus
        
        How does activator stimulates transcription?
        
        The recruitment model argues that the activator’s sole effect is to increase the binding of RNA polymerase to the promoter
        
        An alternative model is to suppose that the activator induces some change in the transcriptional complex; for example, in the conformation of enzymes such as protein kinases, which increases its efficiency.
        
        Mediator
      - DNA - binding domains
        
        The zinc finger
        
        Steroid receptors
        
        The helix-turn-helix motif
        
        amphipathic helix-loop-helix (HLH)
        
        Leucine zippers
  - - - PHO system
      - Nucleosome positions (promoter region)
- - - - Histone acetyltransferases (HATs)
        target lysine > KATs
      - Histone deacetylases (HDACs)