Cellular response to DNA Damage and Repair II Flashcards Preview

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Flashcards in Cellular response to DNA Damage and Repair II Deck (19):
1

TLS

Translesion DNA Synthesis; component of SOS response; In play when DNA damage is extensive

2

Error Prone Repair Def. and Mechanism

1) DNAP III Senses error and halts 2) B-clamp dissociates as well as DNAP III 3) Halting recruits DNAP IV or V (EPP Error prone polymerase) 4) EPP deposits random nucleotides, has no proofreading ability 5) Other Repair mechanisms hopefully will fix damage.

3

When is NHEJ likely to occur?

Mostly during G1, when a sister chromatid is absent

4

When is HEJ likely to occur?

Most likely after S phase when a sister chromatid is available.

5

SOS response in bacteria

1) RecA is normally low 2) Stalling of DNA replication initiates the binding of RecA to ssDNA 3) RecA activated and cleaves LexA 4) cleavge of LexA repressor leads to its inactivation (via activated self proteolysis) 5) Leads to the production of many SOS genes. 6) Once repairs are made. RecA decreases the binding affinity for ssDNA, leads to LexA increase and inhibition.

6

RecA roles

1) represses LexA 2) leads ssDNA to sister chromatid 3) Binds to ssDNA, slightly unwinds it, and leads it to homologous chromosome.

7

RecC

Protein that finds ds breaks and aids in the loading of RecB and RecD (helicases).

8

RecB

3' to 5' helicase activity. Endonuclease activity as well. Produces 3'OH at Chi site

9

RecD

5' to 3' helicase

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Chi sequence

5'-GCTGGTGG-3'

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RecA primary Binding site

Binds ssDNA

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RecA secondary site

Bind dsDNa. Unwinds and checks for homology.

13

RuvA

maintains holiday junction geometry

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RuvB

helicase. Moves junction

15

RuvC

Endonuclease cuts strands to resolve the junction. Separates the two duplex DNAs.

16

Rad51

RecA in eukaryotes.

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Ku proteins

Conserved proteins that are involved in NHEJ. Recognize dsbreaks; recruits DNA PKs; activates Artemis.

18

Artemis

exonuclease that blunts ends to join

19

NHEJ issues

Crude introduces deletions.

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