Cmbm- Exam 1- Regulation Of Gene Expression

Front 1

How many genes are present in the human genome?

Back 1

20,000-25,000

Front 2

What are the two major processes that regulate transcription?

Back 2

1) Regulation of Transcriptional Activators
2) Epigenetic Signals

Front 3

What affect does acetylation have on histones?

Back 3

Acetylation weakens the histone/DNA interaction and allows TFs to access DNA more easily

Front 4

What epigenetic reaction is used to inactivate genes?

Back 4

DNA methylation

*only inactive genes are methylated

Front 5

What protein attracts DNA methylase to methylate DNA?

Back 5

Histone reader/writer protein

Front 6

What is the source of methyl groups for DNA methylation?

Back 6

SAM

*requires folate for its synthesis*

Front 7

What three processes are involved in post-transcriptional regulation?

Back 7

1) Alternative splicing
2) Regulation of mRNA stability
3) RNA editing

Front 8

What type of alternative splicing usually leads to only one version of the protein being expressed in one cell?

Back 8

Regulated Alternative splicing

*Regulated splicing is usually tissue-specific (different splicing of mRNA leads to different proteins in each muscle)

Front 9

What is the most common pathway for mRNA degredation?

Back 9

Deadenylation-dependent pathway

*The poly A tail is shortened by deadenylation, which also triggers decapping and decay of mRNA from 5' to 3' (Exonucleolytic decay)

Front 10

What sequence in the 3' UTR increase the rate of deadenylation of mRNA?

Back 10

AUUUA elements (AREs)

*These elements first trigger deadenylation, then endonucleolytic attack

Front 11

What happens to IRE-BP when high levels of iron are present?

Back 11

Fe binds IRE-BP, changing its conformation so it is released from the TfR mRNA

* IRE-BP is therefore not able to stabilize the IREs and TfR mRNA, leading to mRNA degredation -> less transferrin receptor made

Front 12

What type of mRNA decay occurs when an in-frame stop codon is found before the last exon junction complex?

Back 12

Nonsense mediated decay (RNA surveillance)

* This also occurs for unspliced introns and extended 3'UTRs

Front 13

Where is ApoB48 found?

Back 13

Intestine

Front 14

What protein makes methylated DNA more stable and in a repressed state?

Back 14

Methyl-binding proteins

Front 15

What is the main function of miRNA?

Back 15

Inhibit protein synthesis

Front 16

What mechanism involves deaminase changing a ribonucleotide, which subsequently changes a codon in the mRNA?

Back 16

RNA editing

*Example: A->I in brain changes codon to code for gultamine instead of arginine

Front 17

What type of gene regulation is used for short term-regulation of protein levels?

Back 17

Translational regulation

Front 18

What is the storage protein for iron?

Back 18

Ferritin

Front 19

What happens to the translation of ferritin mRNA when there is a high iron content?

Back 19

Ferritin mRNA is translated in order to store more iron

*IRE is not bound to IRE-BP and 5' Cap is degraded -> mRNA translation (opposite of transferrin mRNA regualtion)

Front 20

What is the action of eIF2B?

Back 20

eIF2B binds the inactive eIF-2-GDP and causes it to release GDP

This allows EIF-2 to bind GTP to form the active eIF-2-GTP (translation initiation)

Front 21

What effect does phosphorylating eIF-2-GDP have on translation?

Back 21

Inhibits translation and protein synthesis

*Phosphorylated eIF-2-GDP forms a stable complex w/ eIF2B -> NO translation

Front 22

What protein does CPEB bind to which in turn inhibits translation by binding eIFs associated with the 5' Cap?

Back 22

Maskin

Front 23

What protein binds to phosphorylated CPEB?

Back 23

CPSF (cleavage and polyadenylation specific factor)

*CPSF recruits Poly A Polymerase, which adds more As to 3' tail

Front 24

During translation, what particle binds a Signal Peptide present at the N terminus of a developing protein and brings it (along with the ribosome) to a receptor on the ER?

Back 24

Signal-recognition particle

Front 25

Name 4 types of post-translational processing.

Back 25

1) Protein sorting
2) Protein folding
3) ER processing
4) Golgi apparatus processing
5) Protein Secretion
6) Proteolytic Processing
7) Protein Degredation

Front 26

What is the function of chaperones?

Back 26

To assist proper folding of newly synthesized or translocating proteins

*Chaperone activity increased by stress

Front 27

Where and when does the first glycosylation of a newly translated protein take place?

Back 27

In the lumen of the ER when the protein is still attached to ER membrane

Front 28

When is the mannose group (present on lysosomal proteins) phosphorylated?
Where are the mannose 6 phosphate receptors located?

Back 28

When it reaches the Cis Golgi

Trans Golgi

Front 29

What disease is caused by a deficiency of the ability to phosphorylate mannose?

Back 29

I-cell disease

Front 30

What type of protein secretory pathway is present in all cells, all the time, and is not regulated?

Back 30

Constitutive secretory pathway

Front 31

Name the three main destinations of proteins in Golgi protein trafficking?

Back 31

1) Lysosomes
2) Plasma membrane
3) Secretory vesicles

Front 32

Where does proteolytic cleavage of newly synthesized proteins take place?

Back 32

Begins in trans-golgi and continues in secretory vesicles

Front 33

What is the function of proteasomes?

Back 33

Proteosomes degrade non-functional proteins

*they are ATP-dependent*

Front 34

When are proteins degraded?

Back 34

1) They are non-functional
2) End of their natural lifespan
3) Their concentration must rapidly change
4) They are foreign

Front 35

What protein attaches to proteins and targets them for degradation in proteasomes?

Back 35

Ubiquitin

Front 36

What complex (enzyme) adds ubiquitin to the protein marked for degradation?

Back 36

Ubiquitin ligase

Front 37

What are the three mechanisms which activate ubiquitin ligase?

Back 37

1) Phosphorylation
2) Allosteric transition (caused by ligand binding)
3) Allosteric transition (caused by addition of protein subunit)

Front 38

What are the three mechanisms which activate degradation signals on proteins?

Back 38

1) Phosphorylation
2) Unmasking by protein dissociation
3) Creation of destabilizing N-terminus