DNA damage and repairDNA damage and repair

William Kaufmann31-325 LCCC 966-8209

william.kaufmann@pathology.unc.edu

The four R’s of human

DNA metabolism

Mechanism of

cytotoxicityof topoIpoisons

TopoII reactions

DNA strand scission by

topoIIpoisons

Sites of alkylation of

DNA

BP adduct on DNA

An arrested replicon

Pathways of DNA repairO6-alkylguanine DNA alkyltransferase

suicide protein transfers methyl group

Base excision repair

glycosylase, AP endonuclease, DNA polymerase, ligase

Nucleotide excision repair

transcription-coupled and global

Cross-link repair

Fanconi’s anemia genes and BRCA2

Double-strand break repair

Homologous recombination and non-homologous end- joining

Heteroduplex and mismatch repair

Post-replication repair; translesion synthesis by pol eta, zeta, iota or kappa

Nucleotide excision

repair

Pathways of repair of DNA double strand breaks

Non-homologous end-joining; DNA-PK, Ku70/80, XRCC1, DNA ligase IV; immunoglobulin and TCR gene rearrangement

Homologous recombination: rad51,52, XRCC2,3,4

Crosslink repair requires

Fanconi’sanemia genes and BRCA2

Familial cancer syndromes

Ataxia telangiectasia - cell cycle checkpoint function, DNA repair. ATM, NBS1, MRE-11

Fanconi’s anemia - DNA repair. BRCA2 and 5 other genes

HNPCC - mismatch repair, hMSH2, hMLH1, PMS2, hMSH6

Xeroderma pigmentosum - nucleotide excision repair and post-replication repair. 8 XP genes

Familial breast cancer I - S and G2 checkpoint responses. BRCA1

Li-Fraumeni syndrome – cell cycle checkpoint function and DNA repair. P53, Chk2

Bloom’s syndrome, Werner syndrome, Rothmund-Thompson syndrome – chromosomal instability. Blm, Wrn, RecQ

Spindle assembly and polyploidization checkpoints

control

colcemid

NHF-neo NHF-E6

P53-dependent G1 checkpoint function

ATM, Nbs1, and Mre11 are required for the IR-induced S checkpoint.

NHF1

0.00

0.05

0.10

0.150.20

0.25

0.30

0.35

0 10 20 30

Sham 1.5 Gy

ATM -/-

0.000.100.200.300.400.500.600.700.80

0 10 20 30

Sham 1.5 Gy

NBS1 -/-

0.00

0.10

0.20

0.300.40

0.50

0.60

0.70

0 10 20 30

Sham 1.5Gy

Mre11 -/-

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0 10 20 30

Sham 1.5 Gy

Nor

mal

ized

3 H C

PM

Fraction Number

ATR is an essential checkpoint kinase

Ataxia telangiectasia- and rad3-related

ATR-null embryos die at day 3 with severe chromosomal damage

Expression of kinase-inactive ATR overrides checkpoint responses to IR and UVC

Cell Cycle CheckpointsCell Cycle CheckpointsMM SSGG11 GG22 MM

G1Delay

G2 Delay

IR

DNA Damage

ATM/ATR

p53 CHK1

p21/14-3-3 CDC25C

Cyclin B1 / CDC2

UV IR

DNA Damage

ATR ATM

p53 CHK2

p21

Cyclin / CDK’s

Plk-1

Crm1

Passive and active inhibition

of DNA replication by

UVC

Mechanisms and consequences of inhibition of DNA replication by UVC

TT TTATR

Chk1

DNA pol η/ζ

DNA dsb

ATM G2 checkpoint

Replicon initiation

Block pol α/δ

TT

NERp53 p48

UVC-induced chromosomal aberrations

Evolution of DNA damage during the cell cycle