) Persistent genomic instability has been observed in the progeny of mammalian cells exposed to ionizing radiation. This instability is manifested as delayed expression of lethal mutations; accumulation of coincidental mutations; and elevated, non-clonal karyotypic heterogeneity. Limited studies with alpha particles have also suggested that high linear energy transfer (LET) radiation is more potent than low LET gamma rays as an inducer of heritable genome instability. The molecular mechanisms underlying radiation-induced heritable genome instability are not known. In the yeast S erevisiae, there is strong evidence that genes of the RAD52 epistasis group, which are essential for DNA double-stand break repair and homologous recombination, are also involved in maintaining the global integrity of the genome. Recently, human homologs of the yeast RAD51 and RAD52 genes (dubbed hhRAD51 and hhRAD52) have been cloned. The hypothesis the applicant proposes to test is that hhRAD51 and hhRAD52 have roles in maintaining genome integrity, such that loss of expression of these genes will exacerbate radiation induced heritable genome instability.
The specific aims are: 1. To determine the effects of hhRAD5l/52 deficiency in human cells on ionizing radiation-induced genome instability, 2. To determine whether alpha or HZE particles are more potent than gamma rays as inducers of heritable chromosomal instability in human cells, and 3. To determine whether a temporal relationship exists between heritable chromosomal instability and the expression of a delayed mutator phenotype. In this application, the applicant will focus on the delayed genome instability induced by high LET radiation, particularly high Z, high-energy (HZE) particles. HZE are an important component of galactic cosmic rays and are of particular concern in regard to manned space missions. The applicant will study radiation-induced genome instability using HZE particles of various energies that reflect differences in particle track structure. Systematic analysis of genome changes as a function of radiation parameters will provide a fundamental basis for the effects of high LET radiation on genome stability.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA074046-05
Application #
6376394
Study Section
Special Emphasis Panel (ZCA1-CRB-X (J1))
Program Officer
Pelroy, Richard
Project Start
1997-09-30
Project End
2002-09-30
Budget Start
2001-04-01
Budget End
2002-09-30
Support Year
5
Fiscal Year
2001
Total Cost
$126,597
Indirect Cost
Name
Lawrence Berkeley National Laboratory
Department
Type
Organized Research Units
DUNS #
078576738
City
Berkeley
State
CA
Country
United States
Zip Code
94720
Donoho, Greg; Brenneman, Mark A; Cui, Tracy X et al. (2003) Deletion of Brca2 exon 27 causes hypersensitivity to DNA crosslinks, chromosomal instability, and reduced life span in mice. Genes Chromosomes Cancer 36:317-31
Lio, Yi-Ching; Mazin, Alexander V; Kowalczykowski, Stephen C et al. (2003) Complex formation by the human Rad51B and Rad51C DNA repair proteins and their activities in vitro. J Biol Chem 278:2469-78
Allen, Chris; Kurimasa, Akihiro; Brenneman, Mark A et al. (2002) DNA-dependent protein kinase suppresses double-strand break-induced and spontaneous homologous recombination. Proc Natl Acad Sci U S A 99:3758-63
Nimura, Yoshinori; Ismail, Sheikh M; Kurimas, Akihiro et al. (2002) DNA-PK and ATM are required for radiation-enhanced integration. Radiat Res 157:562-7
Schild, D; Lio, Y C; Collins, D W et al. (2000) Evidence for simultaneous protein interactions between human Rad51 paralogs. J Biol Chem 275:16443-9
Brenneman, M A; Weiss, A E; Nickoloff, J A et al. (2000) XRCC3 is required for efficient repair of chromosome breaks by homologous recombination. Mutat Res 459:89-97
Cui, X; Brenneman, M; Meyne, J et al. (1999) The XRCC2 and XRCC3 repair genes are required for chromosome stability in mammalian cells. Mutat Res 434:75-88
Liu, N; Lamerdin, J E; Tebbs, R S et al. (1998) XRCC2 and XRCC3, new human Rad51-family members, promote chromosome stability and protect against DNA cross-links and other damages. Mol Cell 1:783-93