Exam #3 Flashcards
What regulates gene expression?
Gene expression is regulated by any mechanism that controls how much mRNA or protein for a given gene is present in a cell
What are some controls for gene expression at translation?
- Regulation of translation is largely controlled at the initiation step.
- These mechanisms black access of the ribosome and the initiator tRNA to the AUG (initiation site)
- These mechanisms often rely on secondary structures produced by the mRNA transcript itself
What happens when you bind a translation repressor protein to the ribosome-binding site on mRNA?
No protein is made
What happens when you increase the temperature of the ribosome-binding site on mRNA?
Protein is made
What happens when there is low iron concentration?
Iron regulatory protein (IRP) binds to the iron-response element (IRE) to prevent translation
What happens when there is high iron concentration?
Free iron binds to the Iron Regulatory protein (IRP), causing it to dissociate from the IRE, allowing the translation of the mRNA to form ferritin
What are the basic steps of gene expression?
- DNA
1) Transcriptional control - RNA transcript
2) RNA processing control - mRNA
3) RNA transport and localization control - mRNA
4) mRNA degradation control –> Inactive mRNA
5) Translation control –> protein
6) Protein activity control - Inactive or active protein
What is the general mRNA half-life in bacteria and more abundant proteins?
Bacteria: <2-3 mins
More abundant: longer than bacteria
Eukaryotic mRNA is degraded by two general mechanisms, which are…
1) Decapping and rapid 5’ > 3’ degradation
2) Shortened poly-A tail and rapid 3’ > 5’ degradation
What is miRNA? What does it do?
- Short RNA sequences that do not code for proteins
- miRNA direct the action of the RNA-induced silencing complex (RISC) to mRNA with complementary sequences to the miRNA
What can miRNA induce?
miRNA can induce mRNA degradation
What is RNA interference (RNAi)?
- A cellular defense mechanism also used by scientists
- Works similarity to miRNA
- Perhaps first discovered in petunia
What does siRNA do in RNAi?
siRNA than function like miRNA with RISC to chew up complementary RNA molecules in the virus genome
What can scientists do to a gene they want to inhibit?
Scientists can introduce dsRNA for the gene they want to inhibit and let Dicer and RISC do the work
What DNA-binding proteins guide nucleases?
- Zinc-finger nucleases (ZFNs)
- Transcription-activator like effector nucleases (TALENs)
What kind of RNA guides nuclease?
- CRISPR-Cas9 system
What is CRISPR-Cas9? What are the parts of it?
- It is an adaptive immunity in bacteria
- CRISPR: clustered regulatory interspaced short palindromic repeats
- Cas9: CRISPR associated 9 (nuclease)
When all else fails, ______ the darn thing!
Degrade
What is a proteasome?
An abundant protease that only proteolyzes proteins marked for destruction with a polyubiquitin tag.
What happens to damaged or otherwise unwanted proteins?
They are degraded by the proteasome
What does E1-E2-E3 ubiquitin ligase do?
It adds ubiquitin into other proteins
What is E1?
ubiquitin activating enzyme
What is the E2-E3 complex?
ubiquitin ligase
