3 genera Steps in the gene expression in prokaryots?
transcription
posttranscription processes
translation
3 regulatory steps in the gene expression in prokaryotes?
regulation of transcription
regulation of posttranscription processes
regulation of translation
6 Steps of regulatory processes of gene expression in eukaryotes?
regulation of DNA transcription
maturation of mRNA
transport of RNA from nucleus + its localization in cytosol
stability of mRNA
posttranslational modifications
Control of gene expression - general principle?
controlling gene expression is often accomplished by controlling transcription initiation
Regulatory proteins bind to DNA to either block or stimulate transcription —> depending on how they intercat with RNA polymerase
Difference between Prokaryotes and Eukaryotes in the control of gene expression?
Prokaryotic organism —> regulate gene expression in rensponse to their environment
Eukaryotic cells —> regulate gene expression to maintain homeostatsis in the organism
What is the structural organization of prokaryotic operon?
operon consists of regulatory region + structural genes
regulatory region: promotor + operator
RNA polymerase binds to promotor —> if not stopped proceeds over operon to transcribe the structural genes
What needs to happen so a “negative regulation” in the transcriprion in prokaryotes occurs?
the repressor (regulatory protein) binds to the operator of the operon of the prokaryote —> transcription does not proceed = negative regulation
General Definition of a “Lac operon”?
the lac operon contains genes for the use of lactose as an energy source
what is the general structure of a lac operon?
1) Regulatory region:
CAP binding site
promotor
operator
2) Structural genes:
lacZ
lacY
lacA
Which structures bind to the different parts of the regulatory region of the lac operon?
CAP binds to the CAP binding site —> this promotes the RNA polymerase binding
RNA Polymerase binds to promotor
Repressor binds to operator —> block RNA polymerase
The coding region of the lac operon of E.coli contains genes for which 3 enzymes?
1) betta-galactosidase:
hyrolyzed the disaccharide lactose into glucosa + galactose
2) Permease
transmembrane symporter that pumps lactose into cell using a proton gradient in the same direction
3) betta-galactoside acetyltransferase (thiogalactoside transacetylase)
acetylates galactose
lac operon of E.coli —> under which conditions are the 3 enzymes coded by the genes of the coding region produced?
all these proteins are produced when lactose is available to the cell but glucose is not.
—> lactose + NO glucose
the 3 enzymes coded by the genes of the coding region of the lac operon of E. coli —> which enzyme is coded by which gene?
Permease —> LacY
betta-galactosidase —> LacZ
b-galactoside acetyltransferase —> LacA
Regulation of Lac operon gene expression at the level of RNA polymerase movement —> 2 possible scenarios
Glucose + NO lactose
Lactose + NO glucose
Regulation of Lac operon gene expression at tle level of RNA polymerase movement —> if glucose but NO lactose is present
glucose + NO lactose = negative regulation
—> repressor (regulatory protein) is formed —> binds to the operator of the regulatory region of the lac operon
—> RNA polymerase moves but cant continue at operator —> Transcription is blocked by the binding of the repessor to the operator
Regulation of Lac operon gene expression at the levek of RNA polmerase movement —> Lactose + NO glucose
lactose + NO glucose = induction of expression
at presence of lactose + no glucose the repressor is formed + addictionally “Allolactose” is formed
allolactose binds to the repressor —> conformtional change of repressor —> repressor can NOT bind to the operator
RNA polymerase can continue to the coding region —> production of the polygenic mRNA
polygenic mRNA translated into the 3 enzymes required for lactose metabolsim
Regulation of Lac operon gene expression at the level of RNA polymerase binding —> general structure
before promotor lies the CAP binding site —> activated CAP needs to bind to CAP binding site so the RNA polymerase can bind to the promotor
low glucose in cell leads to production if cAMP —>if cAMP binds to the Non-active CAP —> CAP is activated
By which system is cAMP produced in prokaryotic cells?
if there is no glucose —> phosphotransferase system (PTS)
regulation of Lac operon gene expression at the level of RNA polymerase binding —> lactose + NO glucose
if there is NO glucose but lactose —> production of cAMP
cAMP binds to inactive CAP —> form cAMP-CAP complexe —> positive regulation
active CAP binds to the CAP binding site —> RNA Polymerase starts to move
the repressor is inactive (no glucose)
RNA polymerase can move —> catabolic induction of gene expression
Regulation of Lac operon gene expression at the level of RNA polymerase binding —> lactose + glucose
lactose + glucose —> there is no production of cAMP
if there is no cAMP thre is no formation of the active cAMP-CAP complex —> does not bind to the CAP binding site
RNA polymerase can Not bind to the promoter —> catabolic repression of gene expression
Trp operon - which genes does it encode?
the trp operon encodes genes for the biosynthesis of tryptophan
trp operon - when is it expressed and when not?
NOT expressed when the cell contains sufficient amounts of tryptophan
trp operon is expressed when levels of tryptophan are low
What negatively regulates the trp operon?
the trp repressor protein
What is the function of the trp repressor protein?
trp repressor binds to the operator to block trancriprion
In which scenario does the trp repressor protein not work?
binding of repressor to the operon requires a corepressor tryptophan —> low levels of tryptophan prevents the repressor from binding to the operon
regulation of gene expression - trp operon —> if there is lack of tryptophan
repressor (regulatory protein) can NOT bind to the operator
RNA polymerase can continue —> enzymes needed for tryptophan synthesis are proced
regulation of gene expression - trp operon —> if there is precents of tryptophan
tryptophan binds to the regulatory protein (repressor) —> changes conformation of repressor so it can bind to the operator
repressor binds to operator —> RNA polymerase can NOT continue
trancription is blocked by the binding of the repressor to the operator
Which structure is required in the controlling of the expression of eukaryotic genes?
Transcription factors
general transcription factors
specific transcription factors
what are general trancription factors reuired for?
general transcriprion factors are required for transcription initiation
required for binding RNA polymerase to DNA
bind to the promotor region of the gene
what are specific transcription factors required for?
specific transcription factors increase transcription in certain cells or in response to signals
3 ways of inducing of transcription factors?
many transcription factors are often found in the cell in an inactive state —> the activity of these factors is induced by:
binding of ligand (an effector molecule)
protein-protein interaction
covalent modification (phosphorylation-dephosphorylation)
specific transcription factors may be receptors for which substances?
lipophilic hormones
how does the activation of transcription factor by binding ligand work?
lipohilic hormone can simple diffuse through cell membrane
lipohilic hormone either binds to cytoplasmic receptor (cytoplasm) which then transfers into nucleus or directly passes into nucleus and then binds to a nuclear receptor
the formed hormone receptor complex dimerizes —> then binds to the hormone response element on DNA
DNA is transcriped inro mRNA —> translation to protein
action of hydrophilic signal molecules?
Metabolic effects of insulin?
mechanism of insulin effect during activation of transcription factor?
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