Adaptive Responses

Question 1

what are environmental stimuli to set off gene regulation?

Answer 1

1. starvation
2. antimicrobial
3. Host cell
4. Surface

Question 2

whats a Stimulon?

Answer 2

Genes expression change in response to stimulus

May involve regulons eg. Reg1, Reg3, Response A

Question 3

whats a regulon?

Answer 3

All the genes that controlled by a particular regulator

eg Response A and Response B genes are part of the Reg1 regulon

Question 4

what are some Transcriptional regulators?

Answer 4

1. Sigma Factors RpoH and RpoE and Sporulation pathway (B. subtilis)
2. Two Component Regulators a large, important family
3. Post transcriptional regulation
   e. g. Escherichia coli unless otherwise stated

Question 5

what are the sigma factors in Escherichia coli?

Answer 5

1.  Primary sigma Factors Family
RpoD Exponential phase
RpoS  Stationary phase
RpoH Heat Shock
RpoE heat shock
FliA flagellum
2. The sigma54 family 
RpoN N Nitrogen limitation

Question 6

how do sigma’s detect an environmental change?

Answer 6

• Promoter will not recruit RNA pol if specific sigma factor is not present or inactive.
• sigma’s have no sensor domain

Question 7

what do Anti-sigma factors do?

Answer 7

1. negatively regulate transcription by binding to sigma stopping sigma programming RNA pol.

Question 8

give two examples of Anti-sigma factors

Answer 8

1. RpoE and RpoH system

2. Sporulation system

Question 9

how do sigma factors Respond to Stress?

Answer 9

1. Alter gene expression
2. Stress regulon members prevent and repair protein damage by re-fold or degradation.
3. up-regulation of  synthesis activity of
   anti- sigma factors.

Question 10

whats the RseABC system?

Answer 10

1. RpoE activated during heat shock –misfolded
   proteins in periplasm.
2. RpoE part of 4 gene operon – rpoE,rseA,B,C
3. RseA inner membrane protein C terminus domain is periplasmic - sensor – N terminus domain is cytoplasmic - inhibitor

Question 11

what is RseA?

Answer 11

• an anti-sigmafactor
  – normal conditions bind & inactivate RpoE
  – rseA mutant –constitutive high expression of rpoE
  – over express RseA –inhibit RpoE
  – Co- purifies with RpoE in vitro

Question 12

what do RseB&C do?

Answer 12

1. RseB: periplasmic interacts with periplasmic RseA domain

2. RseC: inner membrane promotes RpoE activity. anti-anti sigma factor.

Question 13

How do you sense external signal and transduce across a membrane to cytoplasmic Tf?

Answer 13

1. Tether Tf to CM and control activity by proteolytic cleavage
2. Use membrane bound proteases acting sequentially
3. Response is Rapid, Graduated, Insulated from wrong signals

Question 14

how is Activation of RpoE?

Answer 14

1. Activation requires stimulated and Regulated Intramembrane Proteolysis (RIP) of the anti-sigma factor RseA.
2. DegS- inner membrane protease Senses exposed C terminus of DegS misfolded proteins in the periplasm Cleaves periplasmic part of RseA Relieves RseB inhibition of RseP
3. RseP (YaeL)- inner membrane protease Cleaves RseA in membrane to release RseA- RpoE complex into cytoplasm
   RpoE released by cytoplasmic ATP-dependent proteases

Question 15

Activation of RpoH?

Answer 15

1. Activatedinpresenceofmis-foldedproteinsin
   cytoplasm
2. At high temperature rpoH expression is increased via sigmaE but stability also increased
3. Withnormalproteins,
   – DnaJ & K bind to RpoH
   – DnaJ-K-RpoH complex degraded by FtsH
4. Withmis-foldedproteins,
   – DnaK&JdonotbindtoRpoH
   – DnaJ & K bind to mis-folded proteins
   – RpoH not degraded
   – RpoH bind to RNAP & regulon promoters