Repair Machinery for Radiation-Induced DNA Damage
Abstract
Understanding the repair mechanisms for ionizing radiation (IR) -induced DNA damage and having prior knowledge of a patient's radiation-specific repair capacity will help determine which patients will be most responsive to radiation therapy and design more effective treatment regimes. The objective of this work has been to define the contributions of the mammalian protein Apel, and other candidate nucleases, to the repair of IR-induced genetic damage. We are currently constructing cell lines that lack Apel protein and will determine the sensitivity of these mutant cells to various DNA-damaging agents, e.g. IR. In the course of these studies, we generated a mammalian cell line that overexpresses Apel roughly 5 to 8-fold. This line, relative to the non-overexpressing controls, will be used to examine whether Apel operates as a rate-limiting factor in the repair of certain exogenously-induced DNA damages (e.g. abasic sites and 3' -phosphate and phosphoglycolate blocking damages) . Such studies will address the potential value of modulating Apel repair capacity in terms of protecting or sensitizing target cells from the effects of IR anti-cancer treatments. Additionally, we have completed the biochemical characterization of two protein factors, human Sfn and Hem45/Isg2O. Results from these studies indicate that neither protein has a substrate specificity that is consistent with a major role in repairing IR-induced DNA damage. It thus appears that Apel is the predominant (and perhaps only) repair factor for 3' -damages, although alternative less prominent corrective mechanisms must exist. Future studies will focus more on obtaining accurate quantitative determinations of the overall contribution of Apel to 3' -damage repair and IR protection and less on the search for alternative 3' -repair mechanisms.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2000
- Accession Number
- ADA384080
Entities
People
- David M Wilson
Organizations
- Lawrence Livermore National Laboratory