These inhibit transcription and is a negative control.
These increase the rate of transcription. Positive control.
Transcriptional regulation also involves another molecule. These bind to regulatory transcription factor and cause conformational change. They determine whether or not regulatory transcription factor can bind to DNA.
Small effector molecules
What are the two domains in regulatory transcription factor thatt respond to small effector molecules.
Site where proteins binds to DNA. Site specifically for small effector molecule.
What is an Operon?
A cluster of genes under transcriptional control of one promoter.
Transcribed into mRNA, encodes more than one protein, and allows coordinated regulation of a group of genes with a common function.
In E. Coli there is gene that codes for lactose metabolism. What does it look like?
LacP containing LAcZ, LacY, LacA and regulatory sites LacO and CAP site.
THis is part of the gene for lactose metabolism. what is lacP?
THis is part of the gene for lactose metabolism. what is lacZ?
THis is part of the gene for lactose metabolism. what is lacY?
THis is part of the gene for lactose metabolism. what is lacA?
Near the lac promoter are two regulatory sites:?
lacO and CAP site
Regulatory site: operator - provides binding site for repressor protein.
activator protein binding site
THis gene codes for lac repressor. its considered a regulatoiry gene and has its own promotor.
What is going on when Lac repressor protein binds to nucleotides of the. lac operator site preventing RNA polymerase from transcribing lacZ, lacY and lacA. RNA polymerase can bind but not move forward
Lactose is absent
What is going on when Allolactose is a small effector molecule 4 molecules bind to lac repressor to prevent it from binding DNA. Process is induction the lac operon is inducible
Lactose is present
CAP (ctabolite activator protein) is an...
This is a glucose and represses lac operon
binds to activator protein called catabolite activator protein (CAP) or cAMP receptor protein (CRP)
Small effector molecule, cAMP
Glucose inhibits production of cAMP and so prevents binding of
CAP to DNA
Gene regulation involving CAP and cAMP is an example of?
When cAMP binds to CAP, complex binds to CAP site near....
When both lactose and glucose are high, the lac operon is shut off
Glucose uptake causes cAMP levels to drop, CAP does not activate transcription, Bacterium uses one sugar at a time, glucose
When lactose is high and glucose is low, the lac operon is turned on
Allolactose levels rise and prevent, lac repressor from binding to operator, CAP is bound to the CAP site, Bacterium uses lactose
When lactose is low and glucose is high or low, the lac operon is shut off
Under low lactose conditions, lac repressor prevents transcription of lac operon
In E. coli, encodes enzymes required to make amino acid tryptophan. Regulated by a repressor protein encoded by trpR gene
What's going on with tryptophan when the trp repressor cannot bind to operator site and operon genes transcribed?
Tryptophan levels are low
What's going on with tryptophan when the trp operon is turned off?
Tryptophan levels are high
Tryptophan acts as :
A small repressor molecule or corepressor
binds to its operator in the absence of its small effector molecule
binds to its operator only in the presence of its small effector molecule
What is involved with eukarotic transcription
Activators, repressors, modulation, chromatin, and DNA methylation
stimulate RNA polymerase to initiate transcription
inhibit RNA polymerase to initiate transcription
this is when smaal effector molecules, protein-protein interactions, and covalent modifications can modulate activators and repressors
These activator proteins promote loosening up of the region in the chromosome where a gene is located, making it easier for RNA polymerase to transcribe the gene
This usually inhibits transcription, either by blocking an activator protein or by recruiting proteins that make DNA more compact
There are three features of promoters in Eukary.
TATA box, Transcriptional start site, and regulatoryt or responce elements
5 TATAAAA 3, 25 base pairs upstream from transcriptional start site. Determines precise starting point for transcription
Where transcription begins. With TATA box forms core promoter. By itself results in low level basal transcription
Transcription start site
Recognized by regulatory proteins that control initiation of transcription . Enhancers and silencers
regulatory or responce elements
What are the three proteins mediate transcription
An RNA polymerase II, 5 different general transcription factors (GTFs), and large protein complex called mediator
must come together at core promoter before transcription can be initiated
GTFs and RNA polymerase II
assembled GTFs and RNA polymerase II at the TATA box. Form basal transcription apparatus
composed of several proteins. Partially wraps around GTFs and RNA polymerase II. Mediates interactions with activators or repressor that bind to enhancers or silencers. Controls rate at which RNA polymerase can begin transcription
bind to DNA regions called enhancers
bind to DNA regions called silencers
3 ways to control RNA polymerase II
Activators and repressors regulater by binding to GTFs, regulate using a mediator, and recuit proteins that influence DNA packing
DNA is associated with proteins to form compact chromatin. Chromatin packing affects
What happens when chromatin is packed to closely?
transciption is difficult or impossible
What happens when chromatin is packed open.
Access to the DNA is allowed
Some activators diminish DNA compaction near a gene. Recruit proteins to loosen DNA compaction. name them
Histone acetyltransferase and atp-dependent chromatin remodeling enzymes
Methylation can inhibit transcription in two ways, what are they?
Methylation of CpG islands prevent activator and converting chromatin from an open to closed conformation.
In Eukayotes where is gene expression commonly regulated?
Level of RNA processing and translation
What are the benefits of transcription being done at the RNA processing and translation level?
Produce more than one mRNA transcript from a single gene and faster regulation,
What are the alternative splicing of pre-mRNAs?
processed before it becomes mature, and when there are multiple introns and exons splicing occurs in more than one way
These are small RNA molecules that silence the expression of pre-existinf mRNAs.
MicroRNAs (miRNAs or siRNA)
Cut by dicer to release miRNA. Associates with cellular proteins to become. RNA-induced silencing complex (RISC). Upon binding, either
mRNA degraded or, RISC inhibts translation
Another way to regulate translation involves RNA-binding proteins that directly affect translational initiation
To prevent iron toxicity in mammals cell suthesize