Basic research and understanding cancer proneness: the role of DNA repair

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Basic research and understanding cancer
proneness the role of DNArepair

• Raymond Waters
• Pathology Department,
• Welsh School of Medicine

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DNA Damage
Scale of the problem?
Estimated 1,000,000,000,000,000,000 DNA damage
events per adult human each day
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Sources of DNA damage

• Diet
• Sunlight, ionising radiations
• Natural and man-made chemicals in the
  environment
• Natural metabolism of DNA- each cell,
  each day, loses 20,000 bases from its DNA

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What happens if DNA repair is defective?
Defective DNA repair is linked to a number of
cancer-prone conditions
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Diseases associated with defective DNA repair
Ataxia telangiectasia
Blooms syndrome
Fanconi Anaemia
Cockayne syndrome
Hereditary non polyposis colon cancer(HNPCC)
Nijmegen Breakage Syndrome
Werner syndrome
Trichothiodystrophy
Xeroderma pigmentosum
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Examples of cancer-prone genetic diseases with
defects in DNA repair
AT patient
Cockayne patient
XP Patient
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What does this mean for us?

• The cancer prone diseases shown are infrequent
  
• and are the extremes in our population-
• suffers have major defects in DNA repair
• We have little idea as to how smaller
  variations
• in DNA repair amongst the general population
• influence our susceptibility to cancer

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How do we study DNA repair?

• DNA repair has been highly conserved throughout
  evolution
• We can employ model organisms ranging from
  bacteria and yeasts to mouse models of human
  cancer-prone disease and cultured human cells

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What more do we need to know about DNA repair?

• The precise details of the molecular mechanisms
  of most repair pathways are unclear
• Each cell in our body contains DNA tightly
  wrapped like a ball of wool- how do repair
  mechanisms gain access to it?

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Compacting the genome to fit into the nucleus
2mtrs of DNA packaged into each cell of our body!
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To study relationships between repair and
chromosome structure we needed to

• examine DNA damage at individual nucleotides in
  sequences of choice
• see where nucleosomes and regulatory proteins
  bind with DNA at the sequence level
• have an indication if chromatin remodelling
  occurs during transcription and/or DNA repair
• determine what proteins are recruited to
  specific sequences to enable repair

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Technologies

• we developed a methods to
• examine DNA damage at individual nucleotides in
  sequences of choice
• Adapted them to see where nucleosomes and
  regulatory proteins bind with DNA at the sequence
  level
• have an indication if chromatin remodelling
  occurs during transcription and/or repair
• Employ ChIP to examine modifications at
  individual nucleosomes

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Conclusions

• After DNA damage local regions (domains) of
  chromosomes are remodelled to permit access for
  DNA repair
• There is some overlap with how the cell accesses
  genes for transcription BUT when it does it to
  repair silent genes they stay silent i.e
  transcription factors are excluded

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Implications of the research for human health

• How variable is the DNA repair capability amongst
  the general population?
• Does any variability change cancer risk-can we
  estimate it?

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Implications of the research for human health

• Are there other genes that influence DNA repair
  by controlling access of repair complexes to the
  wound up DNA? YES- we have identified some of
  these-Yu et al Proc Natl Acad Sci USA. 102
  8650-8655 (2005)
• How do they impinge on repair and risk?
• Some inhibitors of their products are emerging as
  cancer therapeutics-how do they influence
  repair-can we target specific components?

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DNA Repair Group at CU Medical School

• S.H. Reed-MRC
• C. J. Jones-CRUK, BBSRC
• Y. Teng- MRC PD
• Y. Yu- MRC PD
• S. Yu-MRC PD
• J. Ferreiro- Marie Curie EU fellow
• C. Hawkins- PG
• H. Lui CRUK PD
• Z. Zhou- PG
• A. Irizar MRC PG
• M. Alam
• N. Mikaleva

• H. Zhuang-Jackson
• J. Fisher
• L. Murcett
• J. Smirnova MRC PD
• L. Patorski PG
• Jane Mellor, Oxford
• Jessica Downs, Cambridge
• Ed Louis, Nottingham
• Pierre Thuriaux, Saclay, France
• Leon Mullenders, Lieden, Netherlands
• Antonio Conconi, Sherbrooke, Canada

Funded by MRC, BBSRC, EMBO, Entente Cordial,
Cancer UK