Regulation of Gene Expression Flashcards
Are mRNAs always translated into protein?
no!
Some of them are degraded before they are translated and some of them are translated into protein then modified and/or degraded after that
Depends on how quickly they are being made and destroyed - should be a balance
Are mRNA only good once?
The same mRNA transcript can be used multiple times for minutes or hours before it is degraded
Which factors can control gene expression in transcription?
regulatory elements
promotors
enhancers
chromatin changes
Methylation of cytosine
Which factors control RNA processing?
removal of introns or exons
choice of poly A site
splice sites
transport rate
Which factors regulate translation?
ribosome choice
initiation start codon placement
secondary structure of mRNA
RNA protein interactions
poly A tail length
What affects mRNA degradation?
specific half-life
mRNA is less stable than rRNA or tRNA
What regulates Protein modification and degredation?
modification - assembly of subunits
degradation - ubiquitin - targeted for destruction
N-rule
What is the rate limiting step of transcription?
RNA polymerase binding and intitiation
True or false
Control of gene expression as is relates to RNA polymerase binding and initiation is highly regulated
True!!!
Are promotors Cis or Trans acting?
Cis Acting
What do Promotors do?
They direct transcription of genes located on the same strand of DNA
They are bound by basal transcription factors
What do Transcription Factors do?
They are free to move around the nucleus and regulate the expression of different genes
Are transcription factors cis-acting or trans-acting?
Trans-acting
How do you form the initiation complex for Transciption?
1) Transcription factor recognizes promotor regions (TATA box)
2) transcription factor binds to site
3) REcruits more transcription factor
4) RNA polymerase binds and
5) more transcription factors join in
Which transcription factor is the most important and why?
TFIIH
It’s important because it functions as helicase - helping to unwind the DNA a this site and kinase because it’s an enzyme that phosphorylates - uses nucleotide to transfer a phosphate to another molecule
What’s an enhancer?
DNA sequences that determine how frequently and when transcription occurs
Cis-acting
Can be far away from the promoter too!
Does methylation increase or decrease the rate of transcription?
decrease
What role do Hormones receptors play in gene expression?
hormones can cause different genes in the nucleus to be activated
Type 1 response - steroids activate it
Type 2 Vit A/D and Thyroid hormones turn it on
They alter the rate of transcription and translation in the cell
How do Type 1 Hormone receptors effect Transcription and Translation?
A hormone from outside the cell diffuses accross the membrane into the cytoplasm
Attaches to the receptor in the CYTOPLASM
becomes activated
and inreases the rate of transcription
How does a type II hormone receptor work?
1) A hormone from ouside of the cell inters the outer most layer of the cell
2) It enters the nucleus - diffuses
3) Binds to a receptor
4) Becomes activated
5) which increases the rate of transcription
Which cells are needed for cell signalling?
cytokines
What are cytokines?
small secreted proteins including chemokines and interferons which act to mediate regulate immunity, inflammation, hematopoiesis by cell signally
How do cytokines work in cell signalling/
They bind to specific membrane receptors and singal the cell to alter expression
