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48 Cards in this Set

  • Front
  • Back
Constant, unregulatated transcription
Increased transcription, positive regulation
Decrease transcription, negative regulation
What is the difference between strong and weak promoters?
Strong promoters match the consensus well, while the weak promoters diverge from consensus.
Where does the promoter specificity reside in the RNA polymerase?
Sigma subunit
What do sigma 32 subunits recognize?
Heat shock promoters which are turned on during excessive insult to the cell usually in the form of heat.
Where do the consensus sequences reside in the sigma 70 promoters?
-35 and -10 region
Impeded access of RNA polymerase to the promoter
Enhance access of RNA polymerase to the promoter
Region of the DNA that binds to the repressor.
What kind of mRNA message do operons generate?
Polycistronic mRNA
What are the functions of the lac operon genes?
Encode genes required for use of lactose as a carbon source:
1) Primase - allows for entry
2) B-galactosidase - which cleaves the disaccharides
What is gene codes for the lac repressor? Where is it found?
Lac I which is found upstream lac operon promoter.
Where does the lac repressor bind?
Primary lac operator as well as one of the two secondary lac operators.
What happens in the presence of allolactose?
Allolactose binds to repressor, preventing its binding to the DNA and inducing transcription
How strong is the lac operon promoter? What does this mean for transcription.
The promoter is suboptimal meaning activation is necessary for high levels of transcription.
In the lac operon, how is activation achieved?
CRP helps recruit RNA polymerase to the promoter.
What is the function of the trp operon gene?
Coding protein required for the biosynthesis of trp amino acid.
In the trp operon, what is trp?
Most importantly, in the transcription attenuation of the trp operon, what does the leader peptide contain?
Tandem pair of trp
Region 2,3,4
How does the leader pair sense trp levels?
Translation of tandem pair of trp in the leader peptide requires charged tRNAs carrying the trp amino acid.

If trp is scarce, this pauses translation.
Which pairs in the leader sequence can base pair? What is the function of each pairing?
2 and 3 or 3 and 4 (mutually exclusive)

3 and 4 generates a stem and loop structure that blocks translation.
What prevents the binding of region 2 and 3?
When trp levels are high the ribosomes move quickly and cover up the region 2, preventing its paring with region 3 (which has not even been transcribed)
Which operon regulates completely through attenuation?
Histone Acetly Transferase
Place acetly groups on histones, changing charge, opening up the chromatin and mark chromatin for further opening.
Histone Deacetylase; help close down chromatin
What is the major way of regulation transcription in eurkaryotes? Why?
Activation; Repression does not occur as much because:

1) Eukaryotic genome is too large to synthesize a different repressor for every gene.

2)Repressors are redundant to chromatin masking of promoters.
In eukaryotes, how do we ensure specificity in transcriptional regulation?
Through multiple activators.
Required since the genome is so large and it's likely that one activator may bind incorrectly.
What are the three classes of proteins needed for transcriptional activation?
Basal transcription factor
Basal transcription factors
These are unregulated and recurit RNAP to the promoter.

Rate of transcription is low.

TBP and other TFII
These are sensitive to regulation and bind to DNA at enhancers
These are non-DNA binding and their function is to mediate interactions between RNAP and transactivator.
HMG protein
facilitate looping
Major co-activator in all eukaryotes which interacts with RNAP and transactivators.
How does repression occur in eukaryotes?
They are not bound to a specific operator sequence. Instead, they interfere with activity of mediator, transctivators and of RNAP and mediators.
How are genes coordinately regulated in eukaryotes?
By using the same activators for various genes.
In yeast galactose metabolism, what is the Gal80p?
Represses the function of the activator.
In yeast galactose metabolism, what is the Gal4p
Bound to an UAS and acts as an activator.
What is responsible for removal of repression?
Binding of galactose to Gal3p and the subsequent binding of Gal3p to Gal80p which results in Gal80p not binding Gal4p and the removal of Gal80+Gal3p to the cytosol.
What is meant by the modular structure of the transactivators?
They have regions that are DNA binding and transactivation domains that bind to other proteins.
What are the different domains of a steroid hormone receptor?
-Hormone binding domain
-DNA binding domain via Zn finger
-Transactivation domain which interacts with co-activators
How can phosphorylation modulate transcription?
DNA Binding Activity
Nuclear Translocation (i.e restrict to cytoplasm or brought to nucleus)
What do forms of alternative RNA processing?
Alternative polyadenylation and splicing
What proteins are generated from the same gene based on whether they are expressed in the thyroid or the brain? What allows for this divergenece?
Cacitonin in Thyroid
CGRP in Brain

Alternate polyadenylation and splicing
What enzyme cleavages dsRNA?
a class of miRNA used during development.

st = small temporal
What's the fate of mRNA that forms perfect base pairing with siRNA?
What is the fate of an mRNA that is imperfectly bound to a siRNA?
Translational inhibition, but can also be degraded.