DNA Replication #2 Flashcards

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1
Q

Name four different methods of bacterial regulation fo initiation.

A
  1. Regulatory inactivation of DnaA
  2. Mehtylation
  3. DnaA sequestration
  4. Recycling of DnaA-ADP for DnaA-ATP
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2
Q

Caf1

A

Chromatin assembly factor 1

~ mediates chromatin assembly in DNA replication and DNA repair

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3
Q

SeqA

A

binds to hemi-methylated GATC sites and prevents re-methylation/binding of DnaA
~ only a temporary block - dissociates then process continues unless another SeqA binds

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4
Q

RIDA

A

Regulatory inactivation of DnaA (RIDA)
~ blocks replication initiation in bacteria
~ accelerates active ATP-DnaA being converted to the inactive ADP-bound form

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5
Q

Reverse transcriptase

A

~ DNA pols that copy RNA into DNA

~ ssRNA =template

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6
Q

Telomerase

A

specialised reverse transcriptase

~ made up of protein (TERT) and RNA (template for repeats + role in enzyme activity)

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7
Q

Telomeres

A

simple sequence repeats at the ends of chromosomes to prevent loss of information
~ TTAGGG in humans
~ G-rich

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8
Q

The End-repliclation problem

A

lagging strand synthesis cannot replicate the very end of a linear chromosome
~ not a problem for circular chromosomes

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9
Q

What promotes Okazaki fragment maturation in eukaryotes?

A

Flap endonuclease (Fen1)

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10
Q

What promotes Okazaki fragment maturation in E.coli?

A

DNA pol 1

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11
Q

Polymerase switching (eukaryotes)

A

handover from Pol alpha-primase to pol delta or epsilon

~ facilitated by clamp loading

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12
Q

How does DNA ligase work?

A

~ nucleophilic attack
~ requires nucleotide cofactors:
BACTERIA = NAD+
EUKARYOTES = ATP

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13
Q

What are the clamp loaders in bacteria/eukaryotes?

A
Bacteria = gamma complex
Eukaryotes = Replication factor C (RFC)
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14
Q

What are the sliding clamps in bacteria/eukaryotes?

A
Bacteria = B-protein
Eukaryotes = PCNA
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15
Q

Name the indicator proteins in bacteria/eukaryotes.

A
Bacteria = DnaA
Eukaryotes = ORC
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16
Q

What are the bacteria/eukaryotes DNA primases called?

A
Bacteria = DnaG
Eukaryotes = polymerase-alpha-primase
17
Q

Termination in bacteria DNA replication

A

~ ter site is bound by Tus
~ replication stops
~ DNA pol I fills in un-replicated DNA

18
Q

Name 4 regulatory mechanisms for DNA rep. initiation used in bacteria.

A

~ regulatory inactivation of DnaA (RIDA)
~ methylation of GATC sites by DNA adenine methylase
~ DnaA sequestration (its binds to datA region next to orC)
~ Recycling of DnaA-ADP to ATP (binds to DARS region and acts as a cofactor for the exchange)

19
Q

Name … regulatory mechanisms for DNA rep. initiation used in bacteria.

A

~ formation of pre-replication complex (PreRC)
~ S-phase kinases phosphorylate MCM, Cdc6 + Cdt1 = released and degraded
~ Cdc45-MCM-GINS complex (CMG) unwinds helix at each fork
~ effect of Cdk levels

20
Q

Pre-replication complex (PreRC)

A

~ initiates DNA rep but then inactivates components

~ only forms in G1 as low Cdk levels

21
Q

Regulatory effects of Cdk levels

A
S1 = decrease cdk lvls = allows formation of preRC
G1 = increased cdk lvls = activates preRC