Lecture 8 Gene Regulation Flashcards Preview

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What is the goal of metabolic regulation?

Efficient use of resources


What are the types of metabolic regulation?

Gene regulation

-increase/decrease amount of protein

-slower response


Post-Translational Modification

-Increase/decrease activity of protein by preventing functioning of protein

-Faster response


What are the stages of transcription/translation that gene regulation and post-translational modification can take place?

Gene regulation

-transcription level w/ regulatory proteins

-transcription or translation level w/ RNA based regulation



-after translation....duh


How do we study gene expression at the protein level and at the gene level?

Protein level - reporter genes


Gene level - DNA sequencing


What are reporter genes?

Genes that code for proteins that are easy to detect/measure

-eg. green fluorescent protein


DNA sequencing is used to study gene expression at the gene level. How do we do it?

1. Isolate mRNA from cells

2. Transform mRNA to DNA

3. Determine identity and number DNA Sequences


What are regulatory proteins? What kind of structure do they have?

proteins that bind to DNA They have homodimeric structure that bind in major groove in DNA to interact w/ specific DNA sequences


What is the function of a regulatory protein?

Either START or STOP transcription


-block RNA polymerase=prevent transcription


-Bind RNA polymerase=activate transcription


What are the types of transcription regulation?

Negative control

-repression of mRNA synthesis


Positive control

-activation of mRNA synthesis


How does negative control of transcription work?

When regulatory protein bound to DNA

-Blocks RNA polymerase and prevents transcription


When regulatory protein released from DNA

-transcription possible but not automatic


How are enzymes used in negative control?

Enzyme Repression


-product abundant in cell=no additional synthesis


Enzyme Induction


-substrate present in cell=additional synthesis


Go through arginine synthesis example, arg operon, for negative control repression.

Arginine acts as co-repressor

-when abundant in cell, it binds repressor and blocks transcription

-when not abundant in cell the repressor doesn't block RNA polymerase


Go through lactose degradation example, lac operon, for negative control induction

lactose acts as inducer


When lactose not abundant in cell the repressor binds DNA to block RNA polymerase

-no need for enzyme


When lactose abundant in cell it binds to repressor to release DNA and allow RNA polymerase to proceed

-need enzyme to break down lactose


What happens if ariginine is high or low in cell?  What kind of negative control is this?


What happens if lactose is high or low in cell?  What kind of negative control is this?

ARGININE - Repression

-High=transcription blocked

-Low=transcription proceeds


LACTOSE - Induction

-High=transcription proceeds

-Low=transcription blocked


What is positive control?

When regulatory proteins bound to DNA

-binds RNA polymerase

-activates transcription


When regulatory proteins released from DNA

-transcription possible but NOT automatic


Go through maltose catabolism, mal operon, example of activation positve control

Excess maltose in cell = time to break it down

Limited maltose in cell = no need for enzymes


Maltose Activator protein + Inducer

-Maltose activator protein and inducer bind allowing the complex to bind to activator binding site allowing transcription to proceed


What is the difference between postive and negative control?


-control DNA region = activator-binding site

-located BEFORE promoter



-control DNA region = Operator

-Located AFTER promoter


What is the activator-binding site?

Near the promoter region, where activator protein binds to allow transcription to proceed

-if activator binding site distant from promoter then requires DNA to loop


What are activator proteins?

help RNA polymerase recognize the promoter region and begin transcription

-eg cAMP


What is global control?

single proteins that regulate the expression of multiple operons

-activate/inhibit entire sets of genes


How do E. coli cells choose glucose over other sugars as an energy source?

Single repressor protein, regulons, prevent transcription of group of genes to metabolize other sugars

-alot of glucose present=prevent transcription of other sugar enzymes

-not alot of glucose=allow transcirption of these enzymes


How do microbes sense/respond to environmental conditions?





Other microbes


What are the types of signal molecules that cause microbes to respond to their environment?

Internal signals

-small molecules that permeate membrane

-directly affect transcription


External signals

-large molecules that can't permeate membrane

-require signal transduction to affect transcription


What is an example of internal signals?

Quorum Sensing

-gene expression requires minimum number of bacteria to be present

-Release autoinducer signal molecules that activate transcription of genes


How do external signal molecules work?

Signal transduction

-external signal activates gene expression


Two component regulatory system

-sensor kinase protein in cytoplasmic membrane detects signal and phosphorylates response regulator

-response regulator binds DNA and represses transcription


How can RNA regulate gene expression?





-riboswitches+antisense RNA


No regulatory proteins required


What is attenuation?

occurs AFTER initiation of transcription and BEFORE its completion


Forms alternative structures of RNA

-Form 1 = stem+loop form ahead of RNA polymerase

-transcription blocked

-Form 2 = stem+loop form behind RNA polymerase

-transcription proceeds


What is an example of attenuation?

tryptophan synthesis


What are riboswitches?

Form of RNA-based gene regulation that prevents translation

-signal metabolite binds directly to mRNA

-uses secondary mRNA structures like attenuation


Form 1

-shine-dalgarno unbound

-translation proceeds


Form 2

-shine-dalgarno bound

-translation blocked


What is antisense RNA?

Form of RNA-based regulation

-prevents translation where small RNA, sRNA, binds to synthesized mRNA

-makes double stranded mRNA=no translation b/c cell stops it since only viruses have dsRNA