Vibrio Cholerae-Regulation of Virulence Gene Expression

Question 1

What are the components of ToxRS virulence regulon?

Answer 1

ToxR and ToxS

Question 2

Interview ToxR

Answer 2

Hi, Im ToxR. A protein that acts as the GLOBAL VIRULENCE REGULATOR.
-the product of the toxR gene spans the cytoplasmic membrane

Question 3

Interview ToxS

Answer 3

Hi, Im ToxS. A protein that acts as the environmental sensor product of the toxS gene.
-ALSO spans the cytoplasmic membrane

Question 4

How do you regulate the toxRS operon

Answer 4

toxRS transcription is regulated by temperature

Question 5

What do toxR and toxS do when they’re bored?

Answer 5

They form an OPERONNN

Question 6

What happens at LOW temperature (outside the host)?

Answer 6

• toxRS operon is ON

- ToxR and ToxS synthesized and incorporated into cytoplasmic membrane

Question 7

What happens at HIGH temperature (inside host’s UPPER gi tract)?

Answer 7

• toxRS is OFF
• ToxR and TOxS are NOT synthesized but old proteins are STILL present in the membrane BUT no signal received so ToxR regulon is OFF

Question 8

What happens at HIGH temperature (inside host’s INTESTINES)?

Answer 8

• ToxS recieves a signal unique to the intestine (lumen) environment
• ToxS communicates this information to ToxR
• cytoplasmic domain of ToxR binds TCP-ACF element DNA
• TCP-ACF transcription is activated

Question 9

Who is toxT

Answer 9

toxT is part of the tcp operon

Question 10

How does ToxR get toxT going?

Answer 10

ToxR activates expression of tcp promoter, so it activates toxT transcription and synthesizes lots of ToxT

Question 11

Who is ToxT

Answer 11

an activator that controls most ToxR regulon genes, including tcp operon. Ergo, ToxT AUTOREGULATES.
-ToxT activates transcription factors of many other operons, including ctxA ctxB operon (carried by the lysogenic CTX prophage)
-ToxT also activates
transcription of a pathogenicity island the TCP-ACF element

Question 12

Vibrio Cholerae virulence requires products of genes located within 1/3

Answer 12

the chromosome-the toxRS operon

Question 13

Vibrio Cholerae virulence requires products of genes located within 2/3

Answer 13

a pathogenicity island incorporated within the chromosome, the TCP-ACF element, including toxT

Question 14

Vibrio Cholerae virulence requires products of genes located within 3/3

Answer 14

a temperate or lysogenic bacteriophage-the CTX phage carrying ctxAB

Question 15

ToxR regulon overview

Answer 15

-stimulus = unknown (lumenal in nature)
-sensor = ToxS
-regulator = ToxR
-member genes:
toxT
tcp
acf
ctxAB