Regulation Of Gene Expression/protein Synthesis

Front 1

What are TSF's regulated by what b/c of changes in TSF's?

Back 1

Regulated in response to environmental factors
Signal transduction pathways result in changes in gene expression b/c of changes in TSF's

Front 2

Describe the characteristics of DNA methylation

Back 2

Some genes controlled this way
Assocoated with heritable gene inactivation
Required for X chromosome inactivation
Methylation usually occurs at a ceratin stage of development and/or tissues
Active promotors CANNOT by methylated and methylated promotors CANNOT be activated
Methyl C recruit chromatin and HDAC's to shut off tanscription completely

Front 3

What are some important things about CpG islands?

Back 3

C-G rich areas
Often at the 5' end of housekeeping genes which are normally not methylated
Inappropriate methylation of CpG islands in tummor suppresspr genes and/or genes encoing protein involved in apoptosis has been associated with some cancers

Front 4

Alternative Sploicing and/or Polydenylation

Back 4

Important for getting more then one protein from one mRNA
Major reason have few gens but many proteins

Front 5

Constituitive Alternative Splicing

Back 5

Not particulary regulated, not specific
Several version of a protein may be made in the same cell at the same time
Results from sequence at exon/intron borders dont conform prefectly to consensus makeing it more difficult for snRNP's to recognize

Front 6

Regulated Alternative Splicing

Back 6

More specific usually a tissue specific or developmental specific regulation
Addition or removal of a functional domain
Single cell will express only one version of teh protein at any given time

Front 7

What are the different ways that alternative splicing can result in different proteins?

Back 7

Optional Exon
Optional Intron
Mutually exclusive exons
Internal splice site

Front 8

What are one of the ways you can regulate proteins?

Back 8

Regulated the stability of mRNA which is sometimes faster that regulating at the transcritional level (no waiting for TSF's)

Front 9

Describe the usual/defualt pathway for mRNA degradation

Back 9

Shortening or removal of the poly A tail (deadenylation)
This leads to decay in 3' - 5' direction
Also can cause Decapping 5' end which can lead to decay

Front 10

Decapping Pathway

Back 10

Less common
Decapping starts first and you have degradation mostly from 5' end

Front 11

Endonucleolytic Pathway

Back 11

Less Common
Signal for endonuclease and lose PolA tail all at once whic triggers degradation for the 3' end

Front 12

RNA Surveilance (nonsense)

Back 12

Process by which aberrant transcripts (defective mRNA's)are rapidly degraded with out being deadenylated first
Can Detect: Early nonsense codons, unsplced intron and extended 3' UTR

Front 13

What does the regulation of mRNA stability depnds on?

Back 13

Depnds on sequeces in 3' UTR that increase or inhibit degradation

Front 14

What happens when iron levels are low?

Back 14

Endonucleolytic cleavage of mRNA is blocked which stabilizes the mRNA so more protein can be translated

Front 15

What do both miRNA and siRNA do?

Back 15

Both bind to target sites in the 3' UTR of target mRNA and inhibit protein synthesis

Front 16

miRNA

Back 16

Binds to sequences that are NOT compleatly complementary
One can regulate many mRNA's
If an mRNA has more then one are sequester in P bodies therefore not translated and eventually degraded
Important in cell growth and development

Front 17

siRNA's

Back 17

Bind to sequences that are perfectly complementary
Cause mRNA cleavage and rapid degradation
Protection of cell from viral infection

Front 18

RNA editing

Back 18

Rare mechanism to alter the sequence of mRNA after transcription
Editing of apolipoprotein B

Front 19

Translation Regulation

Back 19

Faster protein adjuestment then transcriptional
Short-term protein regulation
Important for developemtnal regulation
RBC's almost exclusively b/c no nucleus
Intiation is the rate limiting step and site of most regulation

Front 20

Accessibility of 5' cap Initiation of Translation

Back 20

Proteins that stabilize structures in the 5' UTR can repress translation by making the cap structure less accessible to cap-binding protein

Front 21

Phosphorylation of eIF-2-GDP

Back 21

Prevents formation of eIF-2-GTP
Overall inhibition of translational initiation and protein synthesis

Front 22

What can 3' UTR sequeces do for mRNA?

Back 22

Direct the mRNA to regions of the cell where translation is more or less likely to occur

Front 23

Masking

Back 23

Occurs during gametogensis
mRNA's sequestered and stored for later
3' UTR are required for unmasking

Front 24

Two places protein can be synthesized

Back 24

On "free" ribosomes in the cytosol
"Membranous"ribosomes bound to the ER

Front 25

Proteins made on free ribosomes

Back 25

Default=stay in cytosol
Signal for protein to go to mitochondria or nucleus
Post-Translational Tanslocation

Front 26

Proteins made in the ER

Back 26

Default = secretion
Co-translational translocation
Localization depends on signals provided by glycosylation patterns

Front 27

Protein Folding

Back 27

Occurs in ER lumen
Chaperones and Chaperonins
Mild folding varients can usually be controlled but those prone to aggregation can cause problems

Front 28

Chaperone Proteins

Back 28

Bind and stabilie unfolded or partially folded proteins
Preventing degradation ot aggregation

Front 29

Chaperonin Proteins

Back 29

Directly faciliate the folding of proteins

Front 30

Proteasomes

Back 30

Degrade most misfolded proteins

Front 31

I-Cell Disease

Back 31

Patients are unable to phosphoraylate the mannose.
Results in protein being secreted instead of localized

Front 32

Proteasome

Back 32

Degradation occurs
Found in cytosol
Contineous or regulated
Cell to be degraded must have Ubiquitin