BIO 351 Lecture Notes - Lecture 11: Rna Polymerase Ii, Consensus Sequence, Speed Bump

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13 May 2018
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Transcription, RNA Processing, and Translation Objectives
1. Be ale to da DNA ad RNA uleotides ad distiguish the fo eah othe ou do’t eed to da the
seuees of the itoge ases… just the deoiose ad the phosphate
RNA DNA
2. Not all ateial pootes hae the eat sae DNA uleotides ithi the osesus seuee at -10 and -35.
Explain the significance of these sequence differences.
Need consensus to have a generally agreed upon, widely recognized promoter sequence
If there were all the same sequences then they would all have the exact same level of expression
B hagig the seuees, ou affet the affiit of the “iga Fato o TF II D i eukaotes ad that’s
going to allow for different levels of expression
Expression level is coded by -35 to -10 (in prokaryotes)
3. Explain the role of RNA secondary structure in termination of transcription (hairpin)
Termination sequences include inverted repeats
o CpG rich region of mRNA will bend back on itself and make base pairs
o This secondary structure, called a hairpin, acts like a speed bump and makes the RNA Polymerase slow
down to a halt (through a poorly understood mechanism)
o With RNA Polymerase already halted, it just needs to dissociate from the DNA strand
o These base pairs are broken either in a Rho independent or Rho dependent method
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4. Initiation of transcription in eukaryotes is more complex than in prokaryotes, involving many proteins and DNA
sequences. Why do multicellular organisms require more complex regulation of gene expression?
Default epessio i pokaotes is o
Default epessio i eukaotes is off and must go to great lengths to turn them on
o This is likely because eukaryotes are more complicated, have different cell types, have different cell
regions, and need a lot more coordination
o Having all of them off by default, allows the cell to them go through and turn on the ones that only need
to be turned on (or increased) for specific cells in specific regions
o In patiula, the uleus is seletie o hat it allos to tael i ad out, heeas pokaotes do’t
have a nucleus or specialized organelles
5. What are the roles of TFIID in eukaryotic transcription? Distinguish between transcription factors and
transcriptional activators.
Transcription Factors (TFs)
o Help RNA Polymerase II position near the promoter in Eukaryotes
o We did’t ae a lot of the, ut e did ae oe
o TF II D is the primary one that interacts with RNA Polymerase
o It anchors itself around the -25 region and serves as a landing platform for RNA Polymerase to land on
o TF II D and many other TFs are necessary for the proper affinity and binding of RNA Polymerase
Transcriptional Activator Proteins (TAPs)
o Proteins that bind to enhancer regions
o These regions are quite upstream from the start of transcription
o An TAP bound to an enhancer region will bend around and enzymatically interact with RNA
Polymerase, tapping it and giving it the green light to start transcription
6. We have discussed gain/loss of function mutations. How could either of these be explained by changes to
promoter sequences?
Mutations in the promoter or enhancer region could increase or decrease affinity of their corresponding
proteins
Mutation in promoter that makes it unrecognizable LOF
Mutation in enhancer that makes it unrecognizable LOF
Mutation in enhancer that makes for stronger affinity (or perhaps a duplication and the additive effect of
having more enhancer regions) GOF
7. Distinguish between the roles of promoter sequences and enhancer sequences in eukaryotic gene expression. How
do promoters and enhancers differ in terms of their proximity to the coding region of a gene? What proteins bind
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Document Summary

Transcription, rna processing, and translation objectives: be a(cid:271)le to d(cid:396)a(cid:449) dna a(cid:374)d rna (cid:374)u(cid:272)leotides a(cid:374)d disti(cid:374)guish the(cid:373) f(cid:396)o(cid:373) ea(cid:272)h othe(cid:396) (cid:894)(cid:455)ou do(cid:374)"t (cid:374)eed to d(cid:396)a(cid:449) the se(cid:395)ue(cid:374)(cid:272)es of the (cid:374)it(cid:396)oge(cid:374) (cid:271)ases just the (cid:894)deo(cid:454)(cid:455)(cid:895)(cid:396)i(cid:271)ose a(cid:374)d the phosphate(cid:895) Dna: not all (cid:271)a(cid:272)te(cid:396)ial p(cid:396)o(cid:373)ote(cid:396)s ha(cid:448)e the e(cid:454)a(cid:272)t sa(cid:373)e dna (cid:374)u(cid:272)leotides (cid:449)ithi(cid:374) the (cid:862)(cid:272)o(cid:374)se(cid:374)sus se(cid:395)ue(cid:374)(cid:272)e(cid:863) at -10 and -35. Need consensus to have a generally agreed upon, widely recognized promoter sequence. B(cid:455) (cid:272)ha(cid:374)gi(cid:374)g the se(cid:395)ue(cid:374)(cid:272)es, (cid:455)ou affe(cid:272)t the affi(cid:374)it(cid:455) of the ig(cid:373)a fa(cid:272)to(cid:396) (cid:894)o(cid:396) tf ii d i(cid:374) euka(cid:396)(cid:455)otes(cid:895) a(cid:374)d that"s. If there were all the same sequences then they would all have the exact same level of expression going to allow for different levels of expression. Expression level is coded by -35 to -10 (in prokaryotes: explain the role of rna secondary structure in termination of transcription (hairpin) Initiation of transcription in eukaryotes is more complex than in prokaryotes, involving many proteins and dna sequences.

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