Control of Gene Expression 2: Post transcriptional control

Question 1

RNA splicing can be regulated negatively by what? and what does it do?

Answer 1

repressor molecule that prevents splicing machinery access to splice sites

Question 2

How can RNA splicing be regulated positively? and how?

Answer 2

by activating molecule that recruits and helps direct splicing machinery

Question 3

What do mRNAs have to confer stability?

Answer 3

poly A tail

Question 4

What are the steps in regulation by RNA stability?

Answer 4

1. decapping: exposed mRNA degraded from 5’ end

2. mRNA degraded from 3’ end through poly-A tail and into coding region

Question 5

What does ferritin mRNA do?

Answer 5

storage of iron

Question 6

what does TfR mRNA do?

Answer 6

iron absorbance

Question 7

Describe ferritin

Answer 7

intracellular protein
binds thousands of Fe 3+/molecule
found in most cells

Question 8

What is hemosiderin?

Answer 8

granules of ferritin

Question 9

Where is excess of iron stored?

Answer 9

liver
lungs
pancreas

Question 10

What happens during iron starvation?

Answer 10

decrease ferritin mRNA (encodes storage of protein)
cells must transport iron into cells
make more transferrin receptor (TfR) mRNA

Question 11

What happens during iron in excess?

Answer 11

make more ferritin mRNA
transport less iron out of the cell
make less TfR mRNA

Question 12

What are iron responsive elements (IREs)

Answer 12

recognition sites for binding

Question 13

What are iron responsive regulatory protein (IRP)

Answer 13

aconitase

Question 14

What happens when IRP binds to IRE at 5’ ferritin mRNA

Answer 14

no ferritin- translation is blocked

Question 15

What happens when IRP binds to IRE at 3’ transferrin receptor mRNA

Answer 15

transferrin receptor made-mRNA stable

Question 16

What happens if IRP does not bind to IRE at 5’ ferritin mRNA

Answer 16

mRNA made- get ferritin

Question 17

What happens if IRP does not bind to IRE at 3’ transferrin receptor mRNA

Answer 17

RNA degrades and no transferrin receptor made

Question 18

What are noncoding RNAs?

Answer 18

22 nucleotides long that silence expression of specific mRNA targets

Question 19

What are microRNAs?

Answer 19

regulatory RNAs that regulate messenger RNAs

Question 20

Are the changes in microRNA expression causative of disease or responsive to disease?

Answer 20

yes

Question 21

Causative

Answer 21

miRNAS likely to have mutations that cause the disease

Question 22

Responsive

Answer 22

increased miRNA expression down regulates genes in response to disease to limit severity

Question 23

What is found in the involvement of Tourettes syndrome?

Answer 23

1 form of miRNA, SLITRK1 variant

Question 24

What happens if there is a change in recognition sequence on target SLITRK1 mRNA?

Answer 24

increased miRNA binding

Question 25

What is required by proteins to be functional?

Answer 25

post translational modification

Question 26

What are proteins modified by?

Answer 26

protein kinase

Question 27

What is synthesized in dramatic amounts when the temperature is raised?

Answer 27

heat shock proteins (Hsp)

Question 28

Why are Hsp made dramatically when temp is raised?

Answer 28

increase in temperature leads to increase in misfolding proteins and the Hsp help with refolding

Question 29

What does the proteasome do?

Answer 29

removes misfolded proteins, deliberately destroys aberrant proteins

Question 30

How do you recognize a protein for destruction?

Answer 30

ubiquitin removes unfolded or abnormal proteins

Question 31

How does ubiquitin remove abnormal proteins?

Answer 31

with a recognition tag that marks them for destruction

Question 32

Proteasome inhibitors can be used to treat _________

Answer 32

multiple myelomas

Question 33

What is a myeloma?

Answer 33

cancer of plasma cells

Question 34

What is Bortezomib?

Answer 34

inhibitor of proteasome

Question 35

How does bortezomib world?

Answer 35

interacts with 1 proteolytic site-reversibly inhibits proteasome

Question 36

What are four controls of gene expression?

Answer 36

1. coordinated expression of genes: genes don't exist in a vacuum 2. decision for specialization: what kind of cell do I want to be? 3. Methylation and genomic imprinting: what genes get expressed (or not) from mom and dad 4. X chromosome inactivation: even things out XX vs XY

Question 37

What is genomic imprinting?

Answer 37

differential expression of genetic material depending on the parent of origin

Question 38

What is epigenetic?

Answer 38

regulation of expression of gene activity without altering gene structure

Question 39

What causes Prader Willi (PWS) syndrome?

Answer 39

paternal deletion of chromosome 15 in the region 15q11-q13

Question 40

What are the stages of PWS?

Answer 40

stage one: infantile hypotonia; poor suck; feeding difficulties- failure to thrive stage two: hyperphagia (uncontrollable eating), onset of early childhood obesity

Question 41

What is x inactivation?

Answer 41

In females, one of the X chromosomes becomes very condensed and turns into a Barr body, this chromosome is not expressed

Question 42

True or false? MicroRNAS bind to mRNAs to activate the mRNAs to produce large amounts of protein

Answer 42

False