DNA transcription and Translation Flashcards
What are the steps of the Central Dogma?
In nucleus: DNA to RNA through RNA synthesis (transcription) which is produced in the nucleus and travels to the cytoplasm
RNA to Protein through protein synthesis (translation) produced in the cytoplasm
List the ways to regulate protein conc in a cell
Synthesis of primary RNA transcription How to process this RNA into mRNA Post-transcriptional modifications of mRNA Degradation of mRNA Protein synthesis Post-translational modification of protein Targeting and transport of the protein Degradation of the protein
What are the seven processes that affect the steady state concentration of a protein?
1) Transcription initiation: From gene to primary RNA transcript
2) Post-transcriptional processing: pRNA transcript to mRNA
3) RNA stability
4) translational regulation: mRNA to protein
5) Protein modification: Protein to modified protein
6) Protein transport
7) Protein degradation: Modified protein causes positive feedback by releasing Amino acids back to the previous step
The mechanism of posttranscriptional and translation regulation are?
elaborate and interdependent,especially in development
Regulation of posttranscriptional and translation regulation relies on?
Precise protein-DNA and protein-protein contacts
Define a house keeping gene
under constitutive expression
constantly expressed in approximately all cell
Define and give examples of a regulated gene
Levels of the gene product rise and fall with the needs of
the organism.
Such genes are inducible: able to be turned on
Such genes are also repressible: able to be turned off
Explain the process of RNA polymerase binding to promoters
RNA polymerases bind to promoter sequences near the starting point of the transcription initiation
The RNA polymerase promoter interaction greatly influences the rate of transcription initiation
How is the RNA polymerase binding to promoters a major target of regulation?
Regulatory proteins (transcription factors) work to enhance or inhibit this interaction between RNA polymerase and the promoter DNA
What is the consensus sequence found in?
Many E.coli promoters
What do most bacterial promoters include?
Conserved -10 and -35 regions
What do the conserved -10 and -35 region interact with?
the o factor of RNA polymerase
What does substitution in the -10 to -35 region usual reduce?
the affinity of RNA pol for the promoter
What does the upstream element interact with?
The Alpha subunit of RNA polymerase
What are the uses of o factors
Recognize different classes of promoters
Allows coordinated expression of different sets of genes
How does binding other proteins (transcription factors) to promoters regulate transcription in bacteria?
Recognize promoters of specific genes
May bind small signaling molecules
May undergo posttranslational modifications
Protein’s affinity towards DNA is altered by ligand binding or posttranslational modifications
Allows expression of specific genes in response to signals in the environment
How does specifity factors such as o subunits of RNA pol help regulation?
Specificity factors alter RNA polymerase’s affinity for certain promoters
Give an example of regulation by specifity factors such as o subunits of RNA pol
o subunit of E.coli RNA pol:
Most E.coli promoters recognized by o^70
This subunit can be replaced by one of six additional specificity factors
Heat shock will replace o^70 with o^32 and direct RNA pol to different promoters
What does heat shock induce?
Transcription of new products to protect cell
When does heat shock occur?
Bacteria are subject to heat stress
What does heat shock cause?
RNA pol replaces o^70 with o^32
Causes RNA pol to bind to different set of promoters:
Transcription of new products including chaperones that keep proteins in correct conformation, even in heat
What can regulate Activators and repressors?
Small-molecule Effectors
What is the role of repressors?
Reduce RNA pol-promoters interactions or block the polymerase
Bind to operator sequences of DNA:
Usually near a promoter in bacteria but further away in many Eu
What is the role of Effectors?
Can bind to repressor and induce a conformation change
Change may increase or decrease repressor’s affinity for the operator and thus may increase or decrease transcription
What do Activators improve?
Contacts between RNA polymerase and the promoter
What are the binding sites in DNA for activators called?
Enhancers
What are enhancers usually adjacent too?
Promoters
Often adjacent to promoters that are weak (bind RNA polymerase weakly) so the activator is necessary
In Eu, enhancers may be very distant from the promoter
How are repressors involved in Negative regulation?
Repressors binds to DNA and shuts down transcription
Or alternatively signal causes repressor to dissociate from DNA transcription induced
What are the two types of Negative regulation?
Molecular signal causes dissociate of repressor from DNA, inducing transcription
Molecular signal causes binding of respressor to DNA inhibiting transcription
How does Positive regulation involve activators?
Enhance activity of RNA polymerase
Activator binding sites are near promoters that weakly bind RNA pol or do not bind at all
it may remain bound until molecule signals dissociation
Alternatively the activator may only bind when signaled
What are two types of positive regulation
Molecular signal causes dissociate of activator from DNA, inhibiting transcription
Molecular signal causes binding of activator to inducing transcription
DNA looping allows?
Eukaryotic enhancers to be far from promoters
Activators can influence transcription at promoters thousands of bp away.
Looping can be facilitated by?
Architectural regulator proteins
Co-activators may mediate binding by?
Binding to both activator and RNA polymerase
Define an Operon
A cluster of genes sharing a promoter and regulatory sequences.
Genes are transcribed together, so mRNA’s are several genes represented on one mRNA (polycistronic).
What did the Iac operon discovery reveal?
many principles of gene regulation
Three genes for metabolism of lactose are regulated together as a operon:
What is the job of Beta-galactosidase(lacZ)?
Cleaves the lactose to yield glucose and galactose
Three genes for metabolism of lactose are regulated together as a operon:
What is the job of Lactose permease (galactoside permease lacY)?
Transport lactose into cell
Three genes for metabolism of lactose are regulated together as a operon:
What is the job of Thiogalactoside transacetylase (LacA)?
They rely on negative regulation via a repressor
What happens when glucose is abundant and lactose is lacking?
Cells make only very low levels of enzymes for lactose metabolism
Transcription is repressed
What happens when glucose is scarce and cells are fed lactose?
The cells can use it as their energy source
The cells suddenly express the genes for the enzymes for lactose metabolism
Transcription is no longer repressed
A gene called lacl encodes a repressor called?
The lac repressor
