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Microbiota On Mucosal > B3- Replication Of Kinetoplast Dna > Flashcards

B3- Replication Of Kinetoplast Dna Flashcards

1
Q

How many copies of kinetoplast are there

A

1 on the base of flagella

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2
Q

Why are they on flagella base

A

For the energy and motility

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3
Q

How is ktdna constructed

A

5000 minicircles with valency of 3 (link to 3) and also 40 maxi circles in the network forming long strands

(Kinetoplast disc )

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4
Q

What do maxicircles encode like mt dna

A

Rrnase
Energy transduction genes like nadh dehydrogenase, cox subunits, atp synthase

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5
Q

What do these transcripts undergo for maturation

A

Rna editing where u added or deleted

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6
Q

How do mini circles allow this

A

Encode grnas for this

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7
Q

Which conserved 100-200 bp sequence in all mini circles is for leading strand synthesis initiation

A

Universal minicirlce sequences (UMS)

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8
Q

Which site is for Okazaki fragment stsrt site/ lagging strand

A

Hexamer invariant site (6 residuesh

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9
Q

What are the dna structures in minicircles also conserved in very heterogenous minicircles for bending dna

A

A-tracts of 5+ residues for bending dna for organisation

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10
Q

When are the dna networks replicated which differs to mt dna

A

S phase

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11
Q

Explain to hat happens first in replication of minicircles

A

The central zone (closed circles) released from network by topoisomerase II into the kinetoflagellar zone (kfz)

THEN REPLICATED LIKE PLASMIDS (theta structure replication)

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12
Q

Why do nicks form in replication

A

To make sure only replicated once

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13
Q

Where do they go after kfz for further rep help and ligation

A

2 antipodal sites on each end of dna network

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14
Q

Where do they reattach after antipodal site by topoisomerase II

A

Periphery of the network (ends)

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15
Q

Since it was found they reattach at two poles, what are the 2 suggestive ways they then become evenly distributed across network

A

The disc rotates so each point makes contact with the 2 replication proteins on the periphery

Or they attach at the poles then redistribute

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16
Q

What does this explain

A

How at the start there is poles of higher activity during replication (until rotates completely )

  • then even just before division of meshwork/network
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17
Q

How does maxi circle replication occur according to crithidia model

A

Theta structure/rolling circle model like plasmids
Whilst still attached to the network

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18
Q

Where does it originate

A

Conserved sequences like in minicircles ums

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19
Q

What is segregation of kdna done by

A

Tripartite attachment complex (tac)
Meaning it is dependant on flagellar-basal body to segregate it

20
Q

Before division what holds the 2 networks and what cuts them

A

Maxi circle threads
Topo isomersse II

21
Q

What types of filaments in kinetoplast are between the mt membrane down to surface of the network (pass the kfz) (part of tac) - what do they do to help division

A

Unilateral filaments

Rotation of the networks before division occurs

22
Q

What are the filaments attaching basal body to outside of mt membranes (part of tac)

A

Exclusion zone filaments

23
Q

Which cdc2 - yeast related gene in crithidia found in the kt and what does cdc2 do - potential role??

A

CRK gene in crithidia
Mitotic regulation/cell cycle regulation

24
Q

What ss dna binding protein found in crithidia whcih stops winding back to ds dna - potential role in ktdna??

A

Rep protein A

25
Q

Of 5 purified cross linked proteins from crithidia kt, how many found to have a 9aa import sequences suggesting nuclear encoded AND ALSO how many of the proteins have lysine rich regions perfect for dna binding

A

2 lysine rich

3 have import sequences

26
Q

Why was crithidia shown to hve something that resembles dna pol B - potential role in gapnfilling ?

A

Because was same size , had no proofreading/exonucelase activity , and was able to gap fill Okazaki fragment

27
Q

Why would error rate or 1/1200 for pol B explain minicircle sequences

A

Very heterogenous apart from the 3 conserved motifs

28
Q

Why are they so heterogenous

A

Encode many grnas for editing of maxi circle

29
Q

Which 2 topoisomerase a found in crithidia

A

A tetramer localised within kt

Also a hkmodimer mroe local to the antipodal sites (probably for reattachment)

30
Q

Which protein binds ums and also the hexamer invariant site

A

Umsbp

31
Q

Where is it located

A

2 sites of the kfz

32
Q

What does it binding to okazaki site suggest

A

Okazaki gap last repaired. Potentially stop premature repair

33
Q

What is p38 suggested to do in antipodal sites

A

Speculate it allows helicase together with topoI to unwind dna helix

Because p38 binds replication origin

34
Q

Which polymerases in the kfz

A

Pol 1b and 1c

35
Q

Why is pol 1b likely a hlmodimer

A

Synthesises both leading and lagging strand

36
Q

Where is the pol B identified in crithdiia located for gap filling and what does it pair with

A

Antipodal sites and pairs with ligase kappabeta kb to anneal

37
Q

Which helicase needed for primer removal in brucei and is located in antipodal sites

A

Pif5 helicase

38
Q

Which pol and ligase complex in the network for final reannealinf

A

Pol b-pak and ligase ka

39
Q

What 2 primates are in antipodal site and why - suggested by rnai experimentation

A

Primase 1 is for maxi circle rep
Primase 2 for minicircle (rnai causes increase in covalently closed)

40
Q

Which pif helicase necessary for maxi circle formation

A

Pif2

41
Q

Which protease targets pif2 to regulate replication

A

Hslvu

42
Q

What does oxidation of umsbp do to make sure replication only happens in s phase

A

Inactivates it to control reg
By blocking it’s interaction with zinc (it’s a zfb protein)

Only reduced form is in s phase

43
Q

What is the 3rd component of tac

A

The mt membrane

44
Q

Which 2 proteins seem to have effect on correct segregation (based on rnai experiments) of kdna networks and where are they located

A

P166 and aep-1 likely in the unilateral filaments close to the network/kdna

When interfered with it stops correct segregation

45
Q

Are their roles known specifically yet

A

No

46
Q

What do the kfz zones contain vs antipodal

A

Umsbp,Pol 1b and 1c

Antipodal has topo 2, primase 1 and 2, pol beta, ligase kbeta, sse-1, p38, p93

47
Q

Is the role of pol 1C and D known?

A

No but likely involved in maxicircle since pol 1b produces both minicircle strands

Microbiota On Mucosal (22 decks)

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