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' 5 1K-specific repair capacity will help determine which patients will be most responsive to radiation therapy and design more affective 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 - i-fold (AAS-Apel) . In combination with previous findings, our data indicates that Apel activity is not a good prognostic indicator for sensitivity to the alkylating agent methyl methanesulfonate or the oxidizing agent hydrogen peroxide, but may in some circumstances be for IR and bleomycin. Moreover, the AA8-Apel line displays -l.7 fold elevated resistance to the replication-blocking nucleoside analog dioxolane cytidine, a slightly increased resistance to azidothymidine, but normal sensitivity to arabinosylcytosine and 2',3'-dideoxy-2',3'-dihydrothymidine. This is the first cell-based study demonstrating a role for Apel in influencing cellular resistance to anti-cancer/viral antimetabolites. Additionally, we completed the biochemical characterization of two protein factors, human Sfn and Hem45/Isg20, and have found that these proteins are unlikely involved in repairing IR-induced DNA damage. It thus appears that Apel is a predominant repair factor for 3' - damages, although alternative corrective mechanisms exist. Future studies will focus more on obtaining a quantitative determination of the overall contribution of Apel to 3' -damage repair and IR protection.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2001
- Accession Number
- ADA397028
Entities
People
- David M Wilson
Organizations
- Lawrence Livermore National Laboratory