dna damage and repair lecture - unc.edu · dna damage and repair william kaufmann 31-325 lccc...
TRANSCRIPT
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