Transcript Oxidative Stress and Repair

Oxidative Stress and Repair
• Oxidative DNA modifications
Faiez Al Nimer
• Oxidative lipid modifications
Huang Liyue
• Oxidative protein modifications
Sanyal Nikhilesh
• Oxidative DNA and protein damage repair
Melanie Neely Willis
Oxidative DNA damage
Both nuclear and mitochondrial DNA is attacked by ROS
but mtDNA is affected more because it does not contain histones
it is in proximity to ROS generation and has limited antioxidant
repair system
Strand breaks
Reactive oxygen species
Oxidized base
adducts
DNA-DNA and
DNA-protein cross
links
Oxidized base adducts: Hydroxyl
radical
Evans et al, Reviews in mutation research, 2004
8-OH-Gua and Thymin glycol
Guanine: lowest oxidation potential  most oxidized base
Cell viability and disease
For 8-OH-Gua:
Results in C→A and G→T
transversions, leading to mutations
Affects transcription factor binding and
gene expression
Interferes with methylation of i.e.
oncogenes
For thymin glycol:
T→C transitions have been noted
Blocks replication
DNA oxidation:
Neurodegenerative diseases
8-OHDG staining
p62 promoter oxidation
Lovell et al, J Neurochem, 1999
Du et al, Neurobiol of disease,2009
DNA oxidation:
Neurodegenerative diseases
p62 expression
 Absence of p62 induces
cell death
p62 protects cells from oxidative
stress via the antioxidant response
element (ARE)
Du et al, Neurobiol of disease,2009
Oxidative Stress and Repair
• Oxidative DNA modifications
Faiez Al Nimer
• Oxidative lipid modifications
Huang Liyue
• Oxidative protein modifications
Sanyal Nikhilesh
• Oxidative DNA and protein damage repair
Melanie Neely Willis
Lipid modifications by reactive oxygen
species (ROS)
• Overproduction of ROS damages cellular
components, including lipids, leading to
decline in physiological function and cell death
Reaction of ROS with lipids lead to
• Lipid oxidation
• Lipid peroxidation
Lipid Oxidation
• Initiation
– A radical is formed
• Propagation
– Radicals react and transfer their unpaired electron
to other compounds
• Termination
– Two radicals combine to stop the reaction
Adibhatla RM; Hatcher JF. Antioxid Redox Signal.
2010
Lipid peroxidation
Initiation
LH
OH or M=O
L
L + O2
Propagation
LOO
+ LH
LOOH + metal
Commonly measured
decomposition products
LOO
L + LOOH Hydroperoxide
Alkoxy radical
LO
LOO Peroxy radical
Alkanes
Malondialdehyde
4 hydroxynananol
8-isoprostanes
Adibhatla RM; Hatcher JF. Antioxid Redox Signal.
2010
Oxidative Stress and Repair
• Oxidative DNA modifications
Faiez Al Nimer
• Oxidative lipid modifications
Huang Liyue
• Oxidative protein modifications
Sanyal Nikhilesh
• Oxidative DNA and protein damage repair
Melanie Neely Willis
Effects of Reactive oxygen species on Protein backbone
• Oxidation of proteins often targets them for degradation (20S proteasome
and other proteases).
• Several age-related disorders are characterised by Protein oxidation. E.g.
Parkinson’s disease, Amyotropic Lateral sclerosis.
• Product of the oxidation (Peptide alkoxyl radical) is susceptible to cleavage
by diamide or a-amidation pathways.
Redox Biochemistry, Wiley Interscience, 2008; p186
Oxidation of amino acid residue side chain
Redox Biochemistry, Wiley Interscience, 2008; p188
Oxidation of amino acid residue side chains : Tyrosine
•
Tyrosine oxidation can lead to
dityrosine formation.
•
This leads to protein crosslinking.
•
Useful Biomarker for Oxidative
damage and aging.
Tyrosine
Dityrosine
Larios J M et al. J. Biol. Chem. 2001;276:17437-17441
•
Increased levels of dityrosine is found
in rat hearts where Matrix
metalloproteinase-2 (MMP-2) was
induced by cytokines.
Qun Gao C et al. Cardiovasc Res 2003;57:426-433
Oxidation of amino acid residue side chains : Cysteine
Sulfonic acid
Sulfinic acid
Sulfenic acid
R’ - Glutathione or another protein
Green J and Paget MS (2004) Nat Rev Microbiol. 2(12):954-66
Beneficial effects of ROS on Proteins : e.g. DJ-1
H2O2 oxidises the Cys106 (-SH)
to sulfinic acid (-SOOH)
Cys106 oxidation is controlled by its neighbouring environment.
Oxidised Cys106
Partially oxidised
Cys106 (Sulfenic
acid)
Blackinton et al et al. J. Biol. Chem. 2009;284:6476-6485
Beneficial effects of ROS on Proteins : e.g. DJ-1
Cys106 is essential for maintaining
nuclear morphology. Shown here are
M17neuroblastoma cells
Cys106 helps increase Cell
viability under mitochondrial
stress
Blackinton et al et al. J. Biol. Chem. 2009;284:6476-6485
Oxidative Stress and Repair
• Oxidative DNA modifications
Faiez Al Nimer
• Oxidative lipid modifications
Huang Liyue
• Oxidative protein modifications
Sanyal Nikhilesh
• Oxidative DNA and protein damage repair
Melanie Neely Willis
DNA & Protein Repair Enzymes
Oxidation of pyrimidine and purine bases leads
to DNA damage.
Oxidation of methionine and cysteine residues
can lead to protein damage and aggregation.
DNA damage is repaired by several enzymes in
the Base Excision Repair pathway (BER).
Proteins are repaired by methionine sulfoxide
reductases (MsrA, MsrB) and sulfiredoxins.
Base Excision Repair
1. Removal of the damaged
base from the sugar by a
damage-specific glycosylase
2. Processing of the
apyrmidinic-apurinic (AP) site
by an AP endonuclease and
deoxyribosylphosphate lyase.
3. Replacement of an
undamaged nucleotide by
DNA polymerase.
4. Repairing nicks in the DNA
backbone by DNA ligase.
Crystal Structure Shows DNA Bending
Lukianova OA, David SS. A role for iron-sulfur
clusters in DNA repair. Curr Opin Chem Biol.
2005;9:145–151.
Reversibility of Prx Hyperoxidation
Before exposure
After 10 minutes exposure to
H202
Recovery for 4 hours
10 more minutes of exposure
to H202
Recovery for 8 hours
Woo HA, Chae HZ, Hwang SC, Yang KS, Kang SW, Kim
K, Rhee SG.Science. 2003 Apr 25;300(5619):592-4.
Mechanism of reduction of Prx-SO2− by Srx.
Jönsson T J et al. J. Biol. Chem. 2009;284:33305-33310