Dna repair


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  • While wood smoke is similar to second hand tobacco smoke, research findings indicate that second hand wood smoke has potentially an even greater ability to damage your health and the health of your family and loved ones.Comparing tobacco smoke (TS) and wood smoke (WS) using electron spin resonance (ESR) reveals something quite startling. TS does damage in the body for 30 seconds after it is inhaled. WS continues to be chemically active and can cause damage to the cells in the body for 20 minutes or 40 times longer (Pryor, 1992). What does that mean? Some of the components in WS are atoms or molecules in need of at least one unpaired electron to become stable compounds. They are called free radicals. Free radicals interact with your body. They borrow these electrons from the body, leaving body cells unstable - or injured if you will. Some of the cells then die. Other cells are altered and will function differently. The cells give off by products of inflammation that causes a stress on the body. The lungs have an active-transport system that absorbs foreign bodies that are deeply imbedded and cannot be coughed or sneezed up. It pulls the particles into the blood stream for elimination. Inflammation in one part of the body can cause disease in another. Free radicals play a role in a large number of diseases and pathological states. As examples, cancer, aging, heart attack, stroke, diabetes, and Lou Gehrig's disease all have a free radical component to their mechanism of injury. The use of free radical modulators in the prevention and treatment of these diseases is under close investigation at this time including clinical trials.What is the fate of the asbestos-sized, iron coated and or toxic-loaded particles of wood soot and the combustion gases? The WS micro particles "angular and pointed nature distinguished them from usual carbon pigments". They are not going to just 'go away" as wood is primarily cellulose, an insoluble long chain polymer, consisting of 3000 to 5000 glucose residues. Man lacks the enzyme cellulase needed to digest it. How you are personally affected by smoke pollution will depend on more than your age and your genetic make up (or genotype). It will depend on your phenotype. Phenotype is the entire physical, biochemical, and physiological makeup of an individual as determined both genetically and environmentally. In other words, each of us is the sum of our experience. Genetic changes do not just change down through generations (McClintock, 1951), but can occur horizontally (that is, within an organism) and spontaneously. Wood Smoke can alter your DNA.Additional injury occurs due to the physical aspect of the tiny dagger like particles deposited in the respiratory tubes and lung (Ramage, 1987). The asbestos sized particles get to the deepest area in the lung and can't get back out. They are inside the lung. They are digested, encapsulated in the body or they may get moved to the lymph nodes where they get gobbled up by the immune system cells and then can be excreted. However this vacuum function is easily overloaded. It may take weeks or years for this clearance to take place or the smoke may simply be moved to other tissues and organs. The smoke particles are in the way of the work of the lung. The tiniest particles can clump together causing embolism in the tiniest veins causing blockage.Because the lung is a very wet (100% humidity) and warm place, the WS daggers start to swell (Hopke, 1996). Fine particles are like sponges. They become coated with combustion chemicals and also transport molds, bacteria and viruses. Because the wood smoke particle swells up inside of the lung it deposits a larger dose of the toxins and gases from the environment (Hopke, 1996) directly into the blood stream within the nose and lung. The pathway into the body that a chemical takes is dependent on many factors, such as the availability of trace minerals and vitamins and the overload already present from other chemicals. Some of the processes lead to the production of acetaldehyde and chloral hydrate. (Yes! the old Mickey Finn or "knockout" drops.), both of which can cause the toxic brain symptoms seen with Environmental Illness.A small lung biopsy specimen description from a woman who became ill and disabled heating with a wood stove, reads that it contained: "more than two million black fibers per gram of lung tissue. The black fibers included lathe like and grid like structures and bizarre forms. There were no asbestos fibers identified. It was wood (Ramage et al, 1987)." A small portion of the dagger-like pieces of sub-micron wood fiber taken from her lung were iron coated. Fibrocycstic lung disease is literally cystic spaces and blockage of ducts and overgrowth of fibrous tissue in response to scarring, inflammation and infection caused by particles. In fibrocystic lung disease the scarred lung can weigh three times that of a normal lung putting a larger job on the heart that then becomes enlarged as well. It is also called honeycomb lung. It is seen as a result of asbestos, coal, silica, rock exposure and wood smoke exposure.A 1993 Mexican study of women with no other exposure to pollution except for cooking over wood tells us "pulmonary arterial hypertension (from wood smoke) appears to be more severe than in other forms of interstitial lung disease and tobacco related disease (Sandoval et al, 1993)." Sandoval reported chronic bronchitis and hyperinflated lungs. 77% of the patients had right ventricular enlargement, 50% had right-sided cardiac failure or respiratory infections with in the previous year. 97% had difficulty breathing with even slight exertion. The x-rays of the lungs showed fibrosis of lung tissue similar to long-standing inorganic dust exposure such as silicosis and coal worker's pneumoconiosis. Some patients were in end stage interstitial lung disease where the little lung sacs were thickened and formed cystic cavities. One patient died during the study of squamous cell carcinoma (cancer) of the lung. Another already had atypical bronchial cells that indicated early lung cancer. According to the American Lung Association 156,000 Americans will die this year from Lung Cancer.In addition there is long term environmental damage as "Burning 1 kilogram of wood produced as much as 160 micrograms of total dioxins. This result was obtained when various specimens of wood were burned in different stoves. Soot was collected and analyzed by well-designed and documented procedures. Tetrachlorinated, hexachlorinated, heptachlorinated, octachlorinated dioxins were present. The isomers of the dioxins were separated and quantitated. The highly chlorinated dioxins were the major components. In the soot from a series of experiments, their total content ranged from 10 to 167 mg/kg of fuel. The total yields of tetrachlorinated dioxins (TCDDs) ranged from 0.1 to 7.8 mg/kg of fuel."[Science, Vol. 266 Oct. 21, 1994,T.J. Nestrick and L.L. Lamparski, Anal. Chem. 54, 2292 (1982)].Mary J. Rozenberg, 2001
  • Ultraviolet rays frequently rearrange the electrons in adjacent thymine bases, causing them to cross-link together. This type of damage occurs in skin cells every time they are exposed to sunlight. If left unrepaired, or repaired improperly, whatever proteins are coded for by the damaged sequence can malfunction.
  • Ataxia-telangiectasia is inherited, which means it is passed down through families. It is an autosomal recessive trait. This means that both parents must provide a defective gene for the child to have symptoms of the disorder.The disease results from defects in the ataxia telangiectasia mutated (ATM) gene. Defects in this gene can lead to abnormal cell death in various places of the body, including the part of the brain that helps coordinate movement.Male and female are equally affected.
  • Kyphosis is a curving of the spine that causes a bowing or rounding of the back, which leads to a hunchback or slouching posture.
  • Since degenerative diseases, the main health problems in the developed world, are partly caused by DNA damage, it makes sense to diagnose and nutritionally prevent the underlying cause, genome instability
  • (A) Common DNA damaging agents (top), examples of DNA lesions induced by these agents (middle), and the most relevant DNA repair mechanism responsible for the removal of the lesions (bottom). (B) Acute effects of DNA damage on cell cycle progression, leading to transient arrest in the G1, S, G2, and M phases (top) and on DNA metabolism (middle). Long-term consequences of DNA injury (bottom) include permanent changes in the DNA sequence (point mutations affecting single genes or chromosome aberrations that may involve multiple genes) and their biological effects. Abbreviations: cis-Pt and MMC, cisplatin and mitomycin C, respectively (both DNA-cross-linking agents); (6-4) PP and CPD, 6-4 photoproduct and cyclobutanepyrimidinedimer, respectively (both induced by UV light); BER and NER, base- and nucleotide-excision repair, respectively; HR, homologous recombination; EJ, end joining.
  • Dna repair

    1. 1. DNA REPAIR<br />ANAND C.R.<br />MSc. BIOTECHNOLOGY<br />CUSAT<br />
    2. 2. DNA DAMAGE<br />
    3. 3. Wood Smoke Causes Significant DNA Damage<br />Wood smoke particles <br /><ul><li>generate free radicals
    4. 4. cause lipid peroxidation,
    5. 5. DNA damage
    6. 6. NFkappaB activation
    7. 7. TNF-alpha release in macrophages.</li></ul>Polycyclic Aromatic Hydrocarbons, (PAH) adhere to DNA<br />
    8. 8. Types of DNA Damage<br />
    9. 9. Direct DNA Damage<br />
    10. 10. Random photons of ultraviolet (UV) light induce aberrant bonding between neighbouring pyrimidines (thymine & cytosine) bases on the same strand of DNA. The will prevent the replication machine from duplicating the DNA. The cell will die!<br />This type of defect can be readily reversed by a process called photoreactivation. Visible light energy is used to reverse the defect (in bacteria, yeasts, protists, some plants, and some animals but NOT in humans)<br />
    11. 11. Other forms of DNA damage<br /><ul><li>Deamination
    12. 12. An amino group of Cytosine is removed and the base becomes Uracil
    13. 13. An amino group of Adenine is removed and the base becomes Hypoxanthine
    14. 14. An amino group of Guanine is removed and the base becomes Hypoxanthine</li></li></ul><li>Other forms of DNA damage<br />Depurination - the base is simply ripped out of the DNA molecule leaving a gap (like a missing tooth)…<br />
    15. 15.
    16. 16. Repairing Damaged Bases<br />Direct Reversal of Base Damage<br />Excision Repair<br />Base Excision Repair (BER)<br />Nucleotide Excision Repair (NER)<br />Mismatch Repair (MMR)<br />
    17. 17. DNA Repair Pathways<br />Direct Reversal <br />The simplest of the human DNA repair pathways <br />most energy efficient method<br />involves the direct reversal of the highly mutagenic alkylation lesion O6-methylguanine (O6-mG) <br />Carried out by the product of the MGMT gene O6-alkylguanine DNA alkyltransferase (AGT) (O6-methylguanine DNA methyltransferase) <br />
    18. 18. Correction of the lesion occurs by direct transfer of the alkyl group on guanine to a cysteine residue in the active site of MGMT in a "suicide" reaction. <br />The inactivated alkyl-MGMT protein is then degraded in an ATP-dependent ubiquitinproteolytic pathway. <br />
    19. 19. The O6-mG adduct is generated in low levels by the reaction of cellular catabolites with the guanine residues in the DNA.<br />A number of DNA-damaging chemotherapeutic agents attack the O6 position on guanine, forming the most potent cytotoxic DNA adducts known<br />AGT activity correlates inversely with sensitivity to agents that form such O6-alkylguanine DNA adducts<br />
    20. 20. Mechanism of action of AGT inhibition by O6-benzylguanine (BG). <br />BG penetrates the active site pocket of AGT where it comes in contact with the sulfur of cysteine 145. <br />A covalent transfer reaction inactivates the protein<br />.<br />Gerson S L JCO 2002;20:2388-2399<br />
    21. 21. DNA-damaging chemotherapeutic agents<br />Carmustine (BCNU)<br />Temozolomide<br />Streptozotocin<br />Dacarbazine.<br />carmustine<br />Temozolomide<br />dacarbazine<br />Streptozotocin<br />
    22. 22. O6 alkylation by temozolomide and carmustine (BCNU).<br />The methylating agent temozolomide forms O6-methylguanine DNA adducts that induce cell death by invoking mismatch repair. <br />The chloroethylating agent BCNU initially forms O6-chloroethylguanine DNA adducts that then rearrange to a 1,6-ethanoguanine cyclic intermediate followed by a crosslink with the cytosine directly on the opposite strand. <br />
    23. 23. Base excision repair (BER)<br /> Multi-step process that corrects non-bulky damage to bases<br />Oxidation<br />Methylation<br />Deamination<br />spontaneous loss of the DNA base<br />significant threat to genome fidelity and stability<br />
    24. 24. BER has two subpathways: <br />short patch: replaces the lesion with a single nucleotide<br />long patch: replaces the lesion with approximately 2 to 10 nucleotides<br />Both initiated by the action of a DNA glycosylase that cleaves the N-glycosidic bond between the damaged base and the sugar phosphate backbone of the DNA.<br />
    25. 25. DNA repair by base excision<br /><ul><li>A base-specific DNA glycosylase detects an altered base and removes it
    26. 26. AP endonuclease and phosphodiesterase remove sugar phosphate.
    27. 27. DNA Polymerase fills and DNA ligase seals the nick</li></li></ul><li>Nucleotide Excision<br />Same as Base Excision Except that<br />It recognizes more varieties of damage<br />Remove larger segments of DNA (10 -100s of bases)<br />
    28. 28. Nucleotide excision repair<br /><ul><li>a large multienzyme compound scans the DNA strand for anomalities
    29. 29. upon detection a nuclease cuts the strand on both sides of the damage
    30. 30. DNA helicase removes the oligonucleotide
    31. 31. the gap is repaired by DNA polymerase and DNA ligase enzymes</li></li></ul><li>Mismatch Repair (MMR)<br /><ul><li>Mismatch repair deals with correcting mismatches of the normal bases; that is, failures to maintain normal base pairing (A・T, </li></ul> C・G)<br /><ul><li>Recognition of a mismatch requires several different proteins including one encoded by MSH2.
    32. 32. Cutting the mismatch out also requires several proteins, including one encoded by MLH1.</li></li></ul><li>How does the MMR system know which is the incorrect nucleotide?<br /><ul><li>In E. coli, certain adenines become methylated shortly after the new strand of DNA has been synthesized.
    33. 33. The MMR system if detects a mismatch, it assumes that the nucleotide on the already-methylated (parental) strand is the correct one and removes the nucleotide on the freshly-synthesized daughter strand.
    34. 34. How such recognition occurs in mammals is not yet known.</li></li></ul><li>Mismatch Repairing Mechanism<br />
    35. 35. Proteins involved in the DNA repairing of E. coli.<br />
    36. 36. Recombinational Repair<br />This type of repair is much more complicated than is excision repair, and requires many more gene products. The products of a number of these repair genes are induced by radiation damage, and therefore this type of repair requires protein synthesis before it can function. Because of its complexity, this type of repair makes mistakes<br />
    37. 37. Postreplication Repair (recombinational DNA repair) <br />The dots indicate lesions in the DNA.<br /> DNA synthesis proceeds up to a lesion and then skips past the lesion, leaving a gap in the daughter strand. <br /> Filling of the daughter strand gaps with DNA from parental strands by a recombinational process that requires a functional recA gene.<br />Gaps in the parental strands are repaired by repair replication<br />
    38. 38. Recombinational Excision Repair<br />This process occurs in the part of the chromosome that was replicated prior to irradiation, i.e., where two sister duplexes were present before irradiation. <br />After the excision of the lesion, the resulting gap is filled by the same recombinational process<br />
    39. 39. The recombinational repair of excision gaps in E. coli.<br />UV radiation-induced lesions are produced in both the replicated and unreplicated portions of the genome<br />The gaps produced by excision in the unreplicated portion are repaired by the classical methods of nucleotide excision repair <br />The gaps produced in the replicated portion of the chromosome are repaired by a recombinational process that requires both recA and recF (C-D)<br />
    40. 40. Genetic Diseases<br />Defects in the repair system lead to permanent DNA damage causing xeroderma pigmentosum and other genetic diseases. <br />
    41. 41.
    42. 42. Xeroderma Pigmentosum<br />Defects in one of seven genes (XPA-XPG) important in repairing DNA damage caused by ultraviolet (UV) light.<br />Recessive genetic disorder<br />At a young age<br />Multiple basal cell carcinomas (basaliomas)<br />other skin malignancies<br /><ul><li>Most common causes of death </li></ul>metastatic malignant melanoma<br />squamous cell carcinoma<br />
    43. 43. Pathophysiology<br />Defect in (NER)<br />Seven xeroderma pigmentosum repair genes, XPA through XPG, have been identified.<br />In addition to the defects in the repair genes, UV-B radiation also has immunosuppressive effects that may be involved in the pathogenesis of xeroderma pigmentosum<br />
    44. 44. Midwest: 20 min sunlight would kill 50% of cells in culture dish<br />2%-10% UVB reaches basal layer of skin<br />Leffell and Brash, Scientific American, July 1996<br />
    45. 45. Xeroderma pigmentosum variant<br />The defect in this condition is not in NER, but is instead in postreplication repair<br />A mutation occurs in DNA polymerase έ<br />Several immunologic abnormalities have been described in the skin of patients with xeroderma pigmentosum<br />Clinical studies of the skin of patients indicate prominent depletion of Langerhans cells induced by UV radiation<br />
    46. 46. Other defects in cell-mediated immunity <br />impaired cutaneous responses to recall antigens<br />decreased ratio of circulating T-helper cells to suppressor cells<br />impaired lymphocyte proliferative responses to mitogen<br />impaired production of interferon in lymphocytes<br />reduced natural killer cell activity.<br />
    47. 47. XP patients<br />At high risk for skin cancer<br />Must be protected from the sun and other sources of UV radiation<br />With great caution in <br />sun exposure, XP patients<br />can live to middle age<br />
    48. 48.
    49. 49. Cockayne Syndrome<br />Rare autosomal recessive, heterogeneous, multisystem disorder <br />Named after English physician Edward Alfred Cockayne<br />Characterized by:<br />Dwarfism<br />progressive pigmentary retinopathy<br />birdlike facies<br />photosensitivity<br />
    50. 50. Forms of Cockayne syndrome<br />CS Type I, the classic form<br />characterized by normal fetal growth with the onset of abnormalities in the first two years of life. <br />Impairment of vision, hearing, and the central and peripheral nervous system progressively degenerate until death in the first or second decade of life.<br />CS Type II, otherwise known as connatal CS<br />involves very little neurological development after birth. <br />Death usually occurs by age 7. <br />Has also been designated as COFS syndrome<br />subdivided into several conditions (COFS type 1, 2, 3 (which is itself is associated with Xeroderma Pigmentosum) and type 4).<br />
    51. 51. CS Type III <br />rare and characterized by late onset<br />milder than Type I and II.<br />Xeroderma-pigmentosum-Cockayne syndrome (XP-CS) <br />occurs when an individual also suffers from Xeroderma pigmentosum<br />Some symptoms of each <br />disease are expressed.<br />
    52. 52. Genetics<br />Mutations in the ERCC6 and ERCC8 genes<br />The proteins made by these genes are involved in repairing damaged DNA via the transcription-coupled repair mechanism, particularly the DNA in active genes. <br />If either the ERCC6 or the ERCC8 gene is altered, DNA damage is not repaired. As this damage accumulates, it can lead to malfunctioning cells or cell death.<br />
    53. 53. Fanconi Anemia<br />Fanconi anemia is one of the inherited anemias that causes bone marrow failure.<br />It is a recessive disorder.<br />There are at least 11 different mutations causing fanconi anemia.<br />A*, B, C, D1, D2, E, F, G, I, J, and L.<br />It is considered mainly a blood disease.<br />Many patients eventually develop acute myelogenous leukemia at an early age.<br />Patients are very likely to develop squamous cell carcinomas.<br />
    54. 54. Clinical Manifestations<br /><ul><li>Fanconi Anemia characterized by
    55. 55. physical abnormalities
    56. 56. bone marrow failure
    57. 57. increased risk of malignancy.
    58. 58. Physical abnormalities </li></ul>short stature<br />abnormalities of the thumbs, forearms, skeletal system, eyes, kidneys and urinary tract, ear, heart, gastrointestinal system, oral cavity, and central nervous system<br />
    59. 59. Physical abnormalities contd. <br /> 3. Hearing loss<br /> 4. Hypogonadism<br /> 5. Developmental delay<br />Progressive bone marrow failure with pancytopenia typically presents in the first decade, often initially with thrombocytopenia or leukopenia<br />
    60. 60. Diagnosis and Treatment<br />Patients are usually smaller than average.<br />Blood tests may show a low WBC, RBC, and platelet count.<br />Fatigue.<br />Frequent infections.<br />Frequent nosebleeds<br />Easy bruising. <br />Treatments include:<br />Bone marrow transplant.<br />Growth factors.<br />Hematopoietic (blood-stimulating) growth factors are used to stimulate WBC production.<br />Androgens.<br />Male hormones often stimulate the production of RBCs and platelets.<br />
    61. 61. Ataxia-telangiectasia<br />Rare childhood disease that affects the brain and other parts of the body. <br />Ataxia refers to uncoordinated movements, such as walking. <br />Telangiectasias are enlarged blood vessels (capillaries) just below the surface of the skin. <br />Telangiectasias appear as <br />tiny red spider-like veins.<br />
    62. 62.
    63. 63. Complications<br />
    64. 64. Health Comments<br />
    65. 65. A knowledge of optimal intakes for vitamins and minerals that are needed to prevent DNA damage is required<br />"Excessive genome instability, a fundamental cause of disease, is often an indication of micronutrient deficiency and is therefore preventable <br />accurate diagnosis of genome instability using DNA damage biomarkers that are sensitive to micronutrient deficiency is technically feasible <br />it should be possible to optimise nutritional status and verify efficacy by diagnosis of a reduction in genome damage rate after intervention"<br />
    66. 66. z<br />SUMMARY<br />
    67. 67. REFERENCES<br />http://www.rndsystems.com/mini_review_detail_objectname_MR03_DNADamageResponse.aspx<br />http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002369/ <br />http://www.suite101.com/content/defects-in-dna-repair-and-resulting-diseases-a137961<br />Essential cell biology, 2/e ALBERTS BRAY<br />GENES IX BENJAMIN LEWIN<br />
    68. 68. THANK YOU<br />