The molecular nature of mutants induced by X rays is altered by the presence of the radioprotector cysteamine.
The molecular structure of mutants induced in human lymphoblast cells by 500 cGy X rays in the presence of the radioprotector cysteamine (25 mM) has been compared with that induced by an equally mutagenic treatment of 150 cGy X rays alone. Sets of mutants at the hypoxanthine-guanine phosphoribosyl transferase locus were analyzed by Southern blot. Of 24 mutants induced by X rays in the presence of cysteamine, 67% exhibited no change in the restriction fragment pattern and thus were defined as point mutations; 8% appeared to be total gene deletions and 25% were partial deletions or rearrangements. In contrast, among 28 mutants induced by X rays alone (Liber et al., Mutat. Res. 178, 143-153 (1987)), 46% were point mutations, while 50% were total gene deletions and only 1 mutant (4%) was a partial deletion or rearrangement. Thus mutants isolated in the presence of cysteamine consisted of more point mutations and partial deletions/rearrangements, and considerably fewer total gene deletions. These results suggest that cysteamine may protect selectively against processes which lead to large-scale molecular changes.
Liber
H L
HL
Laboratory of Radiobiology, Harvard School of Public Health, Boston, Massachusetts 02115.
Benforado
K
K
Little
J B
JB
D015139:Blotting, Southern; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D003543:Cysteamine / Q000494:pharmacology*; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase; D066298:In Vitro Techniques; D009154:Mutation; D011831:Radiation Genetics
D003543:Cysteamine; D007041:Hypoxanthine Phosphoribosyltransferase