This Week

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This Week

• Chapters 9, 10.1 and 10.4 - 10.7 for reference,
• exam material will be on lecture content for the
  above,
• Chapter 11.5 (Friday).
• Monday Paper,

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Seminarsextra credit

• May 21 Virgin Birth, Centrosomes, and
  Microbes. William Sullivan, Molecular, Cell,
  Developmental Biology, University of California,
  Santa Cruz
• May 28 "Proliferation Caste Formation in a
  Polyembryonic Parasitoid Wasp". Laura Corley,
  Department of Entomology, Washington State
  University
• Wednesdays, 400 PM, BI 212

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Gene Expression

• the processes by which information contained in
  genes and genomes is decoded by cells,
• ...in order to produce molecules that determine
  the phenotypes observed in organisms,
• transcription (post-transcriptional
  modifications),
• translation (post-translational modifications).

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Transcription
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Transcription

• ...the synthesis of mRNA from a DNA template,
• - now it is important to understand when and
  where, as well as how.

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mRNA Synthesis

• Template (DNA) and Promoter,
• Nucleoside triphosphates (NTPs),
• N A,U,G,or C,
• Enzymes (RNA polymerases),
• Energy (as in replication, from phosphate bonds).

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E. coli RNA Polymerase
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RNA Transcriptionprokaryote
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E. coli Promoter Sequencesconcensus sequence
alignment
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Promoter Regions
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Regulation of Transcription(Prokaryotes)

• Regulation of gene expression is often at the
  transcription level,
• Negative regulation,
• inducible,
• repressible,
• Positive regulation

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Negative Regulation(Inducible)
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Negative Regulation(Repressible)
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Positive Regulation
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Eukaryotic Initiation
Transcription is regulated by activators,
repressors, co-activators and basal transcription
factors.
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Promoter Bashing
Modulators of expression can act at great
distances.
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Drosophila Guts and Such
...(c)LE and (d) ID enhancer driven, give rise to
fly appenages.
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Terms

• cis-acting elements
• DNA sequences that serve as attachments sites for
  the DNA-binding proteins that regulate the
  initiation of transcription.

• trans-acting elements
• the DNA-binding proteins that regulate the
  initiation of transcription.

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Chromatin Remodeling
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Post-Transcriptional Events

• RNA processing,
• splicing,
• poly adenylation,
• Alternate RNA processing.

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RNA can be Autocatalytic

• Group I and Group II introns,
• found in mitochondria, chloroplasts, and
  sometimes in bacteria,

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Group II Introns
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Eukaryotic Intron Excision(not autocatalytic)
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Eukaryotic Intron Excision(sequence is important)
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Spliceosomes

• ... small nuclear RNAs (snRNAs)
• RNA molecules that act as catalysts in
  spliceosomes,
• catalytic RNAs that have probably evolved from
  ancient RNA enzymes (ribozymes).
• work in concert with gt 100 proteins to
  facilitate intron identification and removal,
• snRNPs RNA/Protein structures.

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U1 and U2

• U1 binds to the 5 exon/intron junction.
• U2 binds to the adenosine at the branch site.

Think about the required specificity for intron
identification in cells.
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(No Transcript)
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mRNA Processingsplicing
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Polyadenylation
AAUAA concensus poly-A recognition site.
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Alternate mRNA Processing
recognition of different poly-A sites.
alternate splicing.
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Complexity

• Calcitonin gene.

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Central Dogma
DNA
transcription
RNA
(alternately processed)
translation
Protein
?
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Expanded Central Dogma

• Genome... the dynamic complement of genetic
  material in an individual,
• Transcriptome... mRNA component in an
  individual,
• complexity increases resulting from transcription
  control and transcription and post-transcription
  modification,
• Proteome... the protein component of an
  individual,
• complexity increases due to post-translational
  modification, protein-protein interactions, etc.

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Translation

• the synthesis of a polypeptide. This occurs on
  ribosomes using the information encoded on mRNA,
• tRNA molecules mediate the transfer of
  information between mRNA and the growing
  polypeptide.

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Initiationcomplexity
1. Recent reports of alternate translation
start sites indicate that further complexity in
protein production may occur at the translational
level.

• 2. Recent reports of alternate small sub-unit
  specificity affecting translation,
• different eIs,
• different small sub-
• units.

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What to Study?

• What regulates gene expression,
• How is gene expression modulated?
• Transcriptionally,
• Post-Transcriptionally,
• Translationally.