Topic 23, transcription in eukaryotes.ppt.edu

Topic 23, transcription in eukaryotes.ppt.edu - Topic 23...

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Topic 23: Transcription in eukaryotes
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Learning objectives Be able to define the following terms: reporter assay, transfection, cDNA, in vitro, in vivo, transcriptional regulation Be able to explain/list the main differences in eukaryotic vs. prokaryotic gene expression Focus on transcription (slides 4-11) Be able to list the categories of transcripts produced by the 3 eukaryotic RNA polymerases (slide 4; far right column) Be able to describe methods to study transcription and transcriptional regulation & their applications
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Main differences between gene expression in prokaryotes and eukaryotes
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Main differences 1. # of RNA polymerases used: 3 of them in eukaryotes, 1 main polymerase in prokaryotes 2. Complexity of RNA Polymerase: more subunits in eukaryotes 3. Prokaryotic RNA polymerase binds to DNA directly; eukaryotic does not 4. Eukaryotes have a nucleus and must export mRNAs to cytoplasm 5. Eukaryotes have nucleosomes and chromatin; prokaryotes do not 6. mRNA processing only in eukaryotes
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1. # of RNA polymerases used Bacteria: core enzyme + 1 (of 7 different) sigma factor = holoenzyme --Only 1 type of core enzyme per bacterial species --Transcribes all types of RNAs (mRNA, tRNA, rRNA) Transcribe large rRNAs Transcribe tRNAs, small rRNAs, other non-coding RNAs Transcribe mRNAs and other non-coding RNAs # subunits 14 12 17 Categories of transcripts produced
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Figure 15.05: Schematic of the subunit structure of of eukaryotic polymerases I, II, and III, the archaeal RNA polymerase, and bacterial core RNA polymerase. Adapted from Bell, S. D., and Jackson, S. P., Nat. Struct. Mol. Biol. 7 (2000): 703-705. Bacterial RNA polymerase is relatively simple Eukaryotic RNA polymerase has many accessory factors 2. Complexity of RNA Polymerase
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3. Prokaryotic RNA polymerase binds to DNA directly Eukaryotic RNA polymerase (RNAP) does not bind to DNA directly; other factors recruit RNAP to specific DNA sites (transcription factors) --Next class: how does RNAP bind?
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Transcription factors in eukaryotes Eukaryotic RNAP can’t bind to DNA itself Use transcription factors (TF….) to bind to specific promoter sequences Use other transcription factors to recruit RNAP to the right location
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4.
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