Lecture 9 Slides

Question 0

Regulatory genes

Answer 0

Turn genes on and off

Question 1

What are housekeeping genes

Answer 1

Constitutive genes - expressed all the time

Question 2

Four levels of regulation of gene expression

Answer 2

1. Transcription
2. Post transcription
3. Translation
4. Post translation

Question 3

Three ways to regulate gene expression post transcription

Answer 3

RNA processing, eg splicing
Rna degradation
Rna transport, eg nuclear export

Question 4

Half life of prokaryotic rna

Answer 4

Three minutes

Question 5

Half life of eukaryotic rna

Answer 5

Minutes to hours

Question 6

What does regulation depend on during translation

Answer 6

Whether or not ribosome can translate mRNA

Question 7

Three ways to regulate gene expression post translation

Answer 7

Affect protein stability - some proteins denature easily
Some proteins are targeted for degradation
Modifications eg phosphorylation

Question 8

Example of negative control in transcription

Answer 8

Repressing splicing so intron is not removed

Question 9

Positive control example during transcription

Answer 9

Using an activator to make splicing happen

Question 10

At what point in ponytail does mRNA start to degrade

Answer 10

When there are 25 or fewer adenines

Question 11

Is mRNA decamped before degradation

Answer 11

Yes

Question 12

In what direction does degradation happen

Answer 12

5’ to 3’

Question 13

What initiation factors initiate translation

Answer 13

EIF4G and eIF4E

Question 14

What enzyme degrades poly A tail

Answer 14

Deadenylase

Question 15

What is a translation repressor protein

Answer 15

A protein that blocks the start codon AUG

Question 16

How can a newly synthesized protein fold?

Answer 16

1. Correctly folded without help
2. Correctly folded with help of a molecular chaperone
3. Incompletely folded and digested by the proteasome

Question 17

What digests a protein that is incompletely folded

Answer 17

A proteosome

Question 18

What kind of cells have proteosomes in the cytosol

Answer 18

Eukaryotes, archea, and some bacteria

Question 19

What is Ubiquitin ligase

Answer 19

An enzyme that binds Ubiquitin

Question 20

Where is Ubiquitin added to unwanted protein

Answer 20

To side chain, ends with N terminal. Add c terminal end of Ubiquitin.

Question 21

Polyubiquitin

Answer 21

More than one Ubiquitin has been added to unwanted protein

Question 22

What happens to unwanted protein once Ubiquitin has bound to it

Answer 22

It goes to a proteosome, where it is unfolded. Ubiquitin doesn’t go in. Amino acids are recycled.

Question 23

How many amino acids in Ubiquitin

Answer 23

72

Question 24

How many lysine residues in Ubiquitin

Answer 24

Seven

Question 25

What are the two subunits of Ubiquitin ligase? What is their function.

Answer 25

E2- Ubiquitin transferase | e3- recognizes target protein

Question 26

What is E1 unit

Answer 26

It is the carrier of Ubiquitin

Question 27

What does E1 do with the Ubiquitin it carries

Answer 27

It charges E2

Question 28

What do proteosome target proteins have

Answer 28

PEST motif, which is phosphorylated

Question 29

Destruction box

Answer 29

Amino acid sequence required for degradation

Question 30

n-end rule

Answer 30

N-terminal amino acid of a protein determines its half life (likelihood of being degraded)

Question 31

How is Ubiquitin ligase activated

Answer 31

Phosphorylation by protein kinase | Allosteric transition by ligand binding or protein subunit addition

Question 32

How is a degradation signal activated

Answer 32

Phosphorylation by protein kinase Unmasking by protein dissociation Creation of destabilizing N-terminus

Question 33

Density and molecular weight of proteosome

Answer 33

26s | 2.5 MDa

Question 34

Proteosome subunits

Answer 34

``` 19s cap 20s cylinder (active site) ```

Question 35

What is active site of proteosome

Answer 35

20s cylinder

Question 36

What does unfolding and pulling of protein throufh cylinder require

Answer 36

ATP

Question 37

How does target protein attach to proteosome

Answer 37

At unfoldase ring

Question 38

Contents of cap of proteosome

Answer 38

Ubiquitin receptor Unfoldase ring Ubiquitin hydrolase (to release Ubiquitin)

Question 39

Shape of unfoldase ring

Answer 39

Hexameric

Question 40

Is inactivation by polyubiquination reversible

Answer 40

No

Question 41

Cell life cycle phasesq

Answer 41

Interphase - G1, S phase, G2 | M phase- mitosis and cytokinesis

Question 42

What is cyclin

Answer 42

An enzyme whose concentration varies with stages of cell life cycle

Question 43

When is cyclin concentration high? Low?

Answer 43

High in mitosis | Low during interphase