DNA REPAIR IN MAMMALS

DNA repair is a fundamental cellular process that enables organisms to overcome otherwise lethal damage to their genetic material. Our laboratory focuses on the biochemical mechanisms of DNA repair in human cells and is currently investigating four fundamental aspects of the repair process:

1. Mechanism of RNA transcriptional regulation after DNA damage

Alkylating agents and ionizing radiation, which induce DNA breaks, also alter RNA transcription in mammalian cells. We are working towards the identification of previously unknown cellular factors responsible for transcriptional regulation in response to DNA damage.

2. Mechanism of double-stranded DNA break formation

Double-stranded DNA breaks (the most lethal kind of DNA damage) often result when cells are exposed to ionizing radiation. However, the biochemical mechanism underlying the formation of these breaks is poorly understood. This project aims to establish the biochemistry of double-stranded DNA break formation in human cells.

3. Identification of a new class of radiation sensitive individuals

We have recently obtained evidence suggesting that an inefficient DNA repair pathway can increase an individual's sensitivity to the damaging effects of ionizing radiation. We are currently investigating the biochemical basis for the molecular differences in the DNA repair pathway.

4. Physiological role of poly(ADP-ribosyl)ation

Poly(ADP-ribose)polymerase is an abundant nuclear enzyme which is involved in the repair of DNA breaks. This enzyme becomes activated upon binding to DNA breaks and initiates post-translational modification of proteins by adding poly(ADP-ribose)polymers to substrate proteins. Many proteins, including histones as well as poly(ADP-ribose)polymerase itself, are known to be substrates for this enzyme. However, the physiological role of this protein modification has yet to be determined. In this project, we are investigating the role of poly(ADP-ribosyl)ation in response to DNA damage.

These projects are supported by the Medical Research Council of Canada and National Cancer Institute of Canada.

Satoh MS, Hanawalt PC (1996) TFIIH mediated nucleotide excision repair and initiation of RNA transcription in an optimized cell-free DNA repair-RNA transcription assay. Nucleic Acids Res 24 :3576-3582.