Abstracts of Funded Pilots 2010

Mitchell Jung, PhD: "Role of PARP-1 on DNA Damage Response and Repair"

The accumulation of DNA damage and mutations could lead to genomic instability and diseases such as cancer. For instance, mutations in the breast cancer associated (BRCA) 1 and 2 genes are associated with many cases of hereditary cancers including breast and/or ovarian cancer. The BRCA proteins are critical for the homologous recombination pathway, which repairs DSBs. Poly(ADP-ribose) polymerase-1 (PARP-1) is highly efficient in detecting DNA strand breaks through a DNA-break-sensing motif. Activated PARP-1 immediately modifies itself and histones with ADP-ribose polymer by binding to DNA strand breaks. The enzymatic activity of PARP-1 is suggested to facilitate DNA damage repair, and PARP-1-deficient animals and cells with PARP inhibitor show heightened sensitivity to DNA-damaging agents. Recently, inhibition of PARP-1 catalytic activity is shown to be lethal in cells lacking functional BRCA 1 or 2. However, the mechanism whereby PARP-1 enzymatic activity, including targets of the ADP-ribosylation, facilitates the DNA damage response and repair is not well characterized. Our preliminary data within this proposal show that PARP-1 modifies nucleosomal histones with ADP-ribose in response to a DNA-damaging agent, suggesting that ADP-ribosylated histones (ADPr-Hs) may play important roles in the DNA damage response. The overall hypothesis is that DNA damage-induced histone ADP-ribosylation facilitates to recruit DNA repair factors to the DNA damage sites. Major goals of this proposal are to determine the ADP-ribosylation of histones in response to DNA-damaging chemotherapeutic agents and determine DNA repair factors recruited to nucleosomes containing ADPr-Hs.

Specific Aim #1: Determine the level of ADPr-Hs in normal and repair-deficient cells in response to DNA damaging chemotherapeutic agents.

Specific Aim #2: Identify ADP-ribose-associated DNA repair factors in normal and BRCA mutant cells.