Basic research and understanding cancer proneness the role of DNA repair

Basic research and understanding cancer proneness: the role of DNA repair Raymond Waters Pathology Department, Welsh School of Medicine DNA Damage Scale of the problem? Estimated 1,000,000,000,000,000,000 DNA damage events per adult human each day Sources of DNA damage     Diet Sunlight, ionising radiations Natural and man-made chemicals in the environment Natural metabolism of DNAeach cell, each day, loses 20,000 bases from its DNA What happens if DNA repair is defective? Defective DNA repair is linked to a number of cancer-prone conditions Diseases associated with defective DNA repair Ataxia telangiectasia Cockayne syndrome Bloom’s syndrome Fanconi Anaemia Hereditary non polyposis colon cancer(HNPCC) Trichothiodystrophy Xeroderma pigmentosum Nijmegen Breakage Syndrome Werner syndrome Examples of cancer-prone genetic diseases with defects in DNA repair XP Patient Cockayne patient AT patient What does this mean for us?  The cancer –prone diseases shown are infrequent and are the extremes in our populationsuffers 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 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 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? Compacting the genome to fit into the nucleus 2mtrs of DNA packaged into each cell of our body! 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 we developed a methods to: Technologie s  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 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 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? 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 repaircan we target specific components? 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