Messenger RNA

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Messenger RNA

• Todd Metzger
• BMS 265
• May 8, 2009

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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)

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1955 - Goldstein and Plaut
6 min
62 hr
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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

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Translation Leads to Linear Protein Synthesis

• Dintzis 1961
• Reticulocytes analyzed
• Make 90 hemoglobin
• Radiolabeled amino acids incorporated to
  C-terminus only

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1970 - Messenger RNA VisualizedMiller et al
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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
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Yeast RNA pol II
Catalytic core
Positively charged cleft
Active site occurs between the wall and clamp
(shown closed - elongation)
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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

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TFIIS
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Mediator

• Connects transcription factors to basal machinery

Casamassimi 2007
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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
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mRNA Secondary Structure
- No significant differences for human sequences
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mRNA Vaccinations - Direct
Hess et al 2006
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mRNA Vaccinations - Indirect
Hess et al 2006
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