Week 3: Intracellular Signalling - Controlling Sigma Factors

Question 1

What are the 3 examples of controlling sigma factors?

Answer 1

1. oxidative stress
2. control of translation by temp
   3.. spatial segregation

Question 2

How does oxidative stress control sigma factor?

Answer 2

• cytoplasm normally very reducing environment, don’t normally get disulphide bonds forming
• anti-sigma factor RsrA binds sig-R. cant transcribe DNA
• Zn from the RsrA and the oxidative enviro creates disulphide bond
• RsrA is released form sigR and the SigR is free to transcribe genes in order to adapt to the oxidative stress.
• RstA can rebind it and can reset the system.

Question 3

In the cytoplasm, when can disulphide bonds form?

Answer 3

under stress

oxidative stress

Question 4

What is the anti-sigma factor in oxidative stress?

Answer 4

RsrA

Question 5

What is the effect of RsrA binding sig-R?

Answer 5

cant go and transcribe genes

Question 6

When an oxidative stress occur what happens to the RsrA?

Answer 6

th Zn is removed out

Question 7

How can oxidative stress form a disulphide bond?

Answer 7

the ZN is removed out of the RsrA, and oxidative stress can form a disulphide bond.

in the oxidative environment, a disulphide bond can for in the RsrA

Question 8

How is sigR released form RsrA?

Answer 8

the Zn leaves and the RsrA changes confo and the sigmaR is released.

Question 9

How does temp control translation by sigma factor?

Answer 9

At 30 dc, rpoHis transcribed, the mRNA binds and makes hairpins.

The binding site or translation in the sigmaH mRNA is occluded and not free. Hairpin.

When temp increases, the bonds in the mRNA are not strong enough to withstand increase in tempo and melts (open structure)

• ribosome can find ribisome binding site and increase sigma H.
• It can find the core enzyme and transcribe genes for eat shock adaptation.

Question 10

In this case, what is a high and low temp?

Answer 10

low 30 dc
high 42 dc

Question 11

What gene encodes the sigma factor H?

Answer 11

rpoH

Question 12

What happens when rpoH is transcribed at 30 dc?

Answer 12

the mRNA forms hairpins so the translation site is occluded and cannot be transcribed (no heat shock stress)

most of it is degraded

Question 13

What happens to the bonds in the hairpin mRNA when temp increases?

Answer 13

When temp increases, the bonds in the mRNA are not strong enough to withstand increase in tempo and melts (open structure)

• ribosome can find ribisome binding site and increase sigma H.
• It can find the core enzyme and transcribe genes for eat shock adaptation.

Question 14

How does increased temp effect the longevity of sigma H?

Answer 14

many mRNA melt and are transcribed, the system is trying to degrade these and will take longer for sigma H to be degraded as the system has a back log.

In the system for linger.

Question 15

What is sigmaH able to do?

Answer 15

it promotes the system to return to normal and fold proteins etc.

Question 16

What is the example microbe for spatial organisation?

Answer 16

bacillus subtilis

during endosperm

Question 17

What does the spatial separation relate to in bacillus subtilis during endospore?

Answer 17

controls sporulation

Question 18

When will bacillus subtilis trigger sporulation?

Answer 18

starvation

Question 19

What is sporulation?

Answer 19

developmental process, once started you go all the way through.

cant go backwards.

Question 20

What sigma factor is linked to sporulation?

Answer 20

SigF

Question 21

Describe how anti-sigma F etc interact with sigmaF?

Answer 21

Anti-sigma factor F holds sigma F inactive.

But… the anti-anti-sigma factor hold the anti-sigma factor inactive.

1. in vegetative cells sigmaF is held inactive by anti-sigmaF
2. The anti-anti-sigmaF has high affinity for the anti-sigma-F. Pulls it of sigmaF and is degraded.
3. although this pathway is always replenished by transcription and translation of anti-sigmaF .

Question 22

What is the anti-sigmaF factor called?

Answer 22

spoIIAB

Question 23

What i sthe sigma-F operon?

Answer 23

spoIIAA (anti-anti-sigF)
spoIIaAB (anti-sigF)
SIGMA F

Question 24

What is a forespore?

Answer 24

precursor for a spore

Question 25

How does the mother cell pump 1 copy of a chromosome into the forespore?

Answer 25

through a pore,

chromosome always moves the origin of replication into the pore first.

The region of origin is moved across first and then the term site (where the sigmaF operon is)

Question 26

What is the role of the mother cell in sporulation?

Answer 26

help the spore form

Question 27

In the mother cell is the sigmaF heald active or inactive?

Answer 27

inactive

Question 28

In the forespore, is sigma factor F active or inactive?

Answer 28

anti-anti sigma F remove the anti-sigma factor. and sigma is active.

Question 29

Why can the forespore not recycle the anti-sigma factor?

Answer 29

it does not have the genes for transcription and translation so keeps the sigmaF active.

Question 30

How would you describe the sporulation division?

Answer 30

asymmetric

asymmetry of genetic material pumping of the chromosome leads to protein asymmetry

Question 31

How would you test the asymmetry of the of sporulation?

Answer 31

move the part of DNA which is responsible for asymmetry and move to area of origin. and will be moved over first.

Anywhere below that didn’t go in first sporulation occurred

if it (sigmaF operon) was put in the top bit, sporulation didn’t occur.