ANR-05-SEST-0038

Exposure to free radicals (ROS) such those produced by pesticides (such Paraquat) or to radiations produces numerous oxidative lesions on genomic DNA in all organisms. ROS can also be produced endogeneously by cellular oxygen consumption. In the absence of repair, because of ageing or of genetic repair-deficient diseases (like Cockayne syndrome, CS), these lesions accumulate in the cells and eventually give rise to major cellular dysfunction. Because the majority of cells are not replicating in organism, we would like to study the effect of unrepaired DNA lesions on transcription by the RNA polymerase II. It is known in bacteria that pol II can make mistake opposite DNA lesions and produce mutated mRNA in the absence of mutation in the DNA. This results in mutated proteins that can modify seriously the cell metabolism. We have access to a large collection of CS patients (because we are the only laboratory in France to carry out the biological diagnosis of DNA repair-deficient patients) that cannot repair oxidized lesions on transcribed strand of active genes and show major neurological degeneration in less that the first 10 years of their life. Our objectives is to study the CS cells with the idea that the oxidized lesions, produced by exogenous or endogenous ROS are mistranscribed by RNA pol II and are at the origin of mutated proteins than can modify or degenerate their non-replicative cells such neurons. This disease may, as well, represent a model for neurodegenerescence linked to natural aging such that found in Alzheimer or Parkinson patients. We have developed in my laboratory a system of constructed plasmid that contained unique chemically introduced oxidized DNA lesion (such 8-oxo-guanine) on the luciferase gene. This vector cannot replicate in human cells but can be transcribed giving rise to mutated luciferase protein if transcription has been erroneous. The luciferase protein is, of course, a model system to develop the cellular assay, but more appropriate targets will be used later to validate the hypothesis. Such mutations in key proteins (for example, the -synuclein protein for Parkinson patients) can have deleterious effects for the cell metabolism. This work can help to find new drugs to prevent or to treat some specific environmentally-induced-diseases.