Ultrasoft 1.5 keV aluminum K X rays are efficient producers of complex chromosome exchange aberrations as revealed by fluorescence in situ hybridization.
The electron pairs generated by ultrasoft 1.5 keV aluminum K X-ray photons deposit their energy in tracks of length < 70 nm and provide an ideal tool for analyzing the spatial distribution of breaks and misrepair processes. We have undertaken the analysis of changes in chromosome structure produced by aluminum K X rays in untransformed HF12 human fibroblasts in G1 phase using fluorescence in situ hybridization (FISH). Multicolored chromosome-specific DNA probes for chromosomes 1 and 2 and an alpha-satellite pan-centromeric probe were used to examine in vitro radiation-induced chromosome-type exchange aberrations. After mean doses of 0.37-2.93 Gy the relative frequencies of complex exchanges, derived from three or more breaks in two or more chromosomes, ranged from 15-35%. For the classic break-age-and-rejoining theory to hold, very large interaction distances are needed to account for this high frequency of multibreak interactions, unless many sites pre-exist where several different chromosomes come very close together. Alternatively, damaged DNA may be able to interact with adjacent undamaged DNA, obviating the need for large rejoining distances.
Griffin
C S
CS
MRC Radiation and Genome Stability Unit, Harwell, Didcot, United Kingdom.
Stevens
D L
DL
Savage
J R
JR
D000535:Aluminum; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D002869:Chromosome Aberrations; D005347:Fibroblasts / Q000528:radiation effects; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D014965:X-Rays
D000535:Aluminum