dna damage and repair lecture - university of north ... · dna damage and repair ... fanconi’s...
TRANSCRIPT
2
The four R’s of human
DNA metabolism
3
Mechanism of
cytotoxicityof topoIpoisons
4
TopoII reactions
DNA strand scission by
topoIIpoisons
Sites of alkylation of
DNA
5
BP adduct on DNA
An arrested replicon
6
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
7
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
8
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
9
10
Spindle assembly and polyploidization checkpoints
control
colcemid
NHF-neo NHF-E6
P53-dependent G1 checkpoint function
11
ATM, Nbs1, and Mre11 are required for the IR-induced S checkpoint.
NHF1
0.00
0.05
0.10
0.15
0.20
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
0.30
0.40
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
12
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
13
Evolution of DNA damage during the cell cycle