Group 4 - Gene Expression

Teachable Unit: Transcription

Teachable Tidbit: Gene expression in the time of cholera: what’s in the water?

Berenice Aguilar, Brian Couch, Michael Gustin, Kathleeen Matthews, Kate Mouzakis, Dereth Phillips, Les Sommerville, Terri Stoner

http://www.nytimes.com/video/2012/03/31/world/americas/100000001463594/cholera-grips-haiti.html

What are the molecular events leading to cholera toxin gene expression?

Vibrio cholerae toxin protein

2 minute brainstorm

Cholera is caused by the expression of a toxic protein (toxin) produced by the Vibrio cholerae bacteria

What is the first step in gene expression to produce the cholera toxin protein?

Learning Goal:1. Students will understand how changes in the protein/DNA

interface affect transcription

5’toxin mRNA

Learning Outcomes:1. Predict how changes in the protein/DNA interface affect

transcription2. Predict and explain how molecular changes contribute to

cholera toxin production

5’toxin mRNA

Predict and explain why this change in promoter can cause these results?

V. cholerae

straintoxin

promoter sequencetranscription

of toxin mRNAtoxin

proteinproduction

1 GAACTTTCTCG ON +

2 GAACGTTCTCG OFF -

TranscriptionON

Sigma Factor

Promoter

Mutant Promoter

Sigma Factor

TranscriptionOFF

Strain 1

Strain 2

Transcription initiation

V. cholerae

straintoxin

promoter sequencetranscription

of toxin mRNAtoxin

proteinproduction

1 GAACTTTCTCG ON +

2 GAACGTTCTCG OFF -

3 GAACTTTCTCG OFF -

Predict and explain what other factor involved in transcription initiation could give strain 3’s results

TranscriptionON

Sigma Factor

Promoter

Mutant Promoter

Sigma Factor

TranscriptionOFF

Strain 1

Strain 2

Transcription initiation

TranscriptionOFF

MutantSigma Factor

Promoter

Strain 3

Vibriocholerae

StrainToxin promoter

sequenceTranscription of

toxin mRNAToxin

proteinproduction

1 GAACTTTCTCG ON +

2 GAACGTTCTCG OFF -

2* GAACGTTCTCG ON +

Vibrio cholerae strain 2 rapidly mutates to strain 2*. Propose a likely mechanism consistent with your knowledge of protein-DNA interactions (1/2 page, written or drawn, complete and clear)

For your homework (summative assessment)

Learning Goal:1. Students will understand how changes in the protein/DNA

interface affect transcription

Learning Outcomes:1. Predict how changes in the protein/DNA interface affect

transcription2. Predict and explain how molecular changes contribute to

cholera toxin production

5’Toxin mRNA