MOLECULAR ANALYSIS OF THE TK LOCUS IN L5178Y LARGE AND SMALL COLONY MOUSE LYMPHOMA CELL MUTANTS INDUCED BY HYCANTHONE METHANESULFONATE

Mouse lymphoma cells of the L5178Y TK+/-3.7.2C line were exposed to va rying concentrations of the anti-schistosomal drug hycanthone methanes ulfonate. The trifluorothymidine (TFT)-resistant cells fell into two c lasses based on colony size. Southern blot analyses were performed usi ng NcoI-digested DNA from a number of large and small mutant colonies from each treatment group. Two different restriction fragment banding patterns were identified in these analyses, those colonies that contai ned the 6.4 kb NcoI restriction fragment and those that did not. A tot al of 471 mutant colonies were analyzed and 84.5% (398) of these colon ies did not exhibit the 6.4 kb fragment. There did not appear to be a hycanthone methanesulfonate dose response effect in the number of colo nies that did not contain the 6.4 kb fragment among the treated groups . In addition, 82% (154 out of 188) of spontaneous mutants did not con tain the 6.4 kb fragment. The results imply that greater than 80% of a ll spontaneous mutations found in the mouse lymphoma assay regardless of colony size do not contain the 6.4 kb fragment and each may be cons idered to be a large scale mutation. In addition, greater than 80% of the hycanthone induced mutations in the mouse lymphoma assay do not co ntain the 6.4 kb fragment and thus may be considered to be a large sca le mutation.