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Messenger RNA

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									Messenger RNA



  Todd Metzger
    BMS 265
   May 8, 2009
               Nomenclature
• Messenger RNAs (mRNA) describes
  cytoplasmic product
• Pre-mRNA (part of hnRNA) in nucleus is
  processed and exported
• Describe by gene/protein, including isoform
  – or NCBI sequence (NM, natural; XM, in silico)
  – New methods for describing spliced mRNAs
    (Sammeth 2008)
1955 - Goldstein and Plaut


                             6 min




                             62 hr
                 Discovery
• Volkin and Astrachan discovered a new type of
  RNA synthesized following infection of
  bacteria by T2 Bacteriophage (Volkin 1956)
  – Newly synthesized RNA mirrored composition of
    T2 DNA
• Brenner, Jacob, and Meselson found that only
  RNA, and not ribosomes, were newly
  synthesized following infection (1961)
  – The term messenger RNA was coined
    Translation Leads to Linear Protein
                 Synthesis

• Dintzis 1961
• Reticulocytes analyzed
  – Make ~90% hemoglobin
• Radiolabeled amino acids incorporated to C-
  terminus only
1970 - Messenger RNA Visualized
          Miller et al
                  Biogenesis

• Enzymatic Reaction by RNA Polymerase
  – RNA Pol II in eukaryotes
• Involves Initiation Factors (TFIIB,D,E,F,H) and
  Mediator Complex
• Core RNA polymerase II is 12 subunits, 500
  kDA, highly conserved
  – 10 subunit catalytic core



                                  Woychik 2002, Sims III 2004
                 Yeast RNA pol II
Catalytic core                                   Positively charged cleft




     Active site occurs between the wall and clamp (shown closed - elongation)
                Transcription

• Template DNA, 5 GTFs, and RNA pol II
  associated to form pre-initiation complex
  – TFIID contains the TATA-box binding protein (TBP)
  – TFIIE and -H melt DNA
• CTD phosphorylation is required for
  dissociation of initiation factors and entrance
  to the elongation phase
• TFIIS allows stalled transcription to continue
  – Reverse procession followed by cleaved of RNA
TFIIS
                  Mediator
• Connects transcription factors to basal
  machinery




                                        Casamassimi 2007
     mRNA Secondary Structure

• Many mRNAs can code for the same protein
• Made program to scramble codons while
  preserving base content
• Looked at 50 bp structures




                                        Katz 2003
mRNA Secondary Structure




 - No significant differences for human sequences
mRNA Vaccinations - Direct




                        Hess et al 2006
mRNA Vaccinations - Indirect




                         Hess et al 2006

								
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