1. Altering the genetic message: Mutation Cancer.
Chapter 17
Altering the genetic message:
Mutation
Cancer.

2. = DNA Damage + DNA Repair.
MUTATIONS
= change in the genetic message
= change in the nucleotide sequence of a gene
= DNA Damage + DNA Repair.
1. Types of mutations
2. Causes of DNA damage
3. DNA (damage) repair

3. Types of mutations. A. Gene mutations a. point mutations
or base-pair substitution
b. frame-shift mutations
B. Chromosomal mutations
(duplication, inversion, deletion,
translocation)

5. Causes of DNA damage. (tautomeric shift, deamination,
1. Spontaneous
(tautomeric shift, deamination,
depurination, looping-out)
2. Oxidation
3. Chemical
- base-pair analogs
- base-modifying agents
- intercalating agents
- agents that cause ‘bulky’ lesions
4. Physical: - UV light
- X-ray

6. Causes of DNA damage. - tautomeric shift - deamination - depurination
1. Spontaneous
- tautomeric shift
- deamination
- depurination
- strand slippage/looping-out

7. Tautomeric shift of bases
Common Form
Uncommon Form

8. Tautomeric shift leads to altered base pairing.

9. Depurination of DNA
Apurinic sites

10. De-amination of cytosine or methyl-cytosine.

14. Strand slippage during DNA replication
5’TACGGAC 3’
3’ATGCCTGACTTTGC 5’
Newly synthesized DNA
Template DNA
5’TACGGACTG 3’
3’ATGCCTGACTTTGC 5’ T
Newly synthesized DNA loops out, …
5’TACGGACTGAAACG 3’
3’ATGCCTGACTTTGC 5’ T
… resulting in the addition of one nucleotide in the new strand.

15. Strand slippage during DNA replication
5’TACGGAC 3’
3’ATGCCTGACTTTGC 5’
Newly synthesized DNA
Template DNA
5’TACGGACTG 3’
3’ATGCCTGCTTTGC 5’
Template DNA loops out, … A
… resulting in the omission of one nucleotide in the new strand.
5’TACGGACGAAACG 3’
3’ATGCCTGCTTTGC 5’ A

17. Causes of DNA Damage 2. Oxidative damage
(Respiration, Mixed function oxidases, Inflammation)

18. Causes of DNA damage. 3. Physical

20. UV-Light
(254 – 260 nm)
Pyrimidine dimers
Gross distortion
DNA molecule

22. Malignant Melanoma

24. Causes of DNA damage. 3. Physical
There are two main ways radiation can damage DNA inside living cells. Radiation can strike the DNA molecule directly, ionizing and damaging it. Alternately, radiation can ionize water molecules, producing free radicals that react with and damage DNA molecules.

25. Causes of DNA damage. 4. Chemical - base-pair analogs
- base-modifying agents
- alkylating agents
- base deaminating
- intercalating agents
- agents that cause ‘bulky’ additions

26. Causes of DNA damage
4. Chemical:
Base Analogs
Miss-pairing

28. Alkylating agents add alkyl groups  Cause altered base pairing
E.g., Ethyl-methane-sulfonate (mustard gas),
Nitroso-guanidine.

29. Base deamination
E.g., nitrous acid, bisulfite

31. Intercalating agents Actinomycin Ethidium Bromide Acriding Orange
Tetracycline
Proflavine
Intercalating agents

32. Bulky additions grossly distort the DNA

33. Aflatoxins
… ‘bulky’ additions, gross distortions of the DNA

35. Benzo (a) pyrene

36. Error-prone DNA repair
Cellular Responses to DNA damage
Error-free DNA repair
Apoptosis
Error-prone DNA repair
Mutation

37. DNA Repair: 1. Direct correction of DNA repair
a. Proofreading of DNA polymerase
b. Repair of alkylating damage
2. Repair involving excission of base pairs
a. General excission repair system (UvABC)
b. Repair by glycosylases and
AP endonucleases
c. Mismatch-repair system
d. SOS-repair system

38. Proofreading Capacity of DNA Polymerase

40. Repair by Alkyl-transferases

41. General Excision repair system

43. Xeroderma pigmentosa:
Deficiency of the general excision repair system.

46. Glycosylase/ AP endonuclease
Repair system

47. Repair by DNA glycosylase
and AP endonucleases.

48. Mismatch Repair System

49. Hereditary Non-Polyposus Colon-rectal Cancer (HNPCC)

50. Error-prone repair by end-joining.

51. Altering the genetic message: Cancer.
Chapter 17
Altering the genetic message:
Cancer.

52. Cancer Independent of growth signals Tissue invasion metastasis
Insensitive to growth inhibitors
Sustained angiogenesis
Cancer
Changed energy metabolism
Limitless replicative potential
Avoid apoptosis

53. Normal cells
Cancer cells loose contact inhibition, grow on top of each other, and become rounded.

54. Normal
Cancer

55. Normal
(contact inhibition)
Cancer

60. Rous sarcoma virus

62. J. Michael Bishop (1936 - ) and Harold E
J. Michael Bishop (1936 - ) and Harold E. Varmus (1939 - ) won the Noble Prize in 1989 for proving that viruses contain a cancer-causing gene derived from the genome of the organism they infect. Specifically, they showed that chicken Rous Sarcoma Virus (RSV) carried an oncogene called v-src and this gene was an intronless version of a normal chicken gene called c-src
Nobel Prize 1989

63. Chicken Rous Sarcoma Virus (RSV) carried an oncogene called v-src and this gene was an intronless version of a normal chicken gene called c-src.

66. Active tumor suppressor gene(s) Inactive tumor suppressor gene(s)
DNA Damage +
DNA Repair
Active tumor suppressor gene(s)
Proto-oncogene(s)
MUTATIONS
Oncogene(s)
Inactive tumor suppressor gene(s)
Gain-of-function
Dominant phenotype
Loss-of-function
CANCER
Recessive phenotype

71. Retinoblastoma. S-phase EF2 Rb Cdk2-cyclin E DNA mRNA DNA polymerase P+
DNA
mRNA
DNA polymerase
S-phase

77. CANCER:
A multi-hit process of mutations accumulating in proto-oncogenes and tumor suppressor genes.

79. Familial Adenomatous Polyposis Coli

80. Colonoscopy Results

82. JB Weitzmann and Nosh Yaniv Nature 1999, 400 p401

83. What causes cancer? 1. Environmental carcinogens
- chemical (e.g., cigarette smoke)
- physical (e.g., UV radiation)
2. Host carcinogens (e.g., inflammation)
3. Viruses:

85. TUMOR VIRUSES
Papiloma virus
Hepatitis B virus
Human Herpes virus 8 (Kaposi)
Human Herpes virus 4 (Epstein Bar)
Human T lymphotropic virus

90. This woman has hepatitis B and is suffering from liver cancer
This woman has hepatitis B and is suffering from liver cancer. She was a Cambodian refugee and died 4 months after she arrived in a refugee camp (average life expectancy after diagnosis of liver cancer is 6 months)

91. Kaposi syndrome: Human Herpes Virus 8)

92. Cutaneous B cell lymphoma

93. HTLV Leukemia

94. The End.