Cells L1210 variants

Nuclear ADPRT activity is present in the variant 3 cells and is stimulated by the addition of deoxyribonuclease. 3-aminobenzamide inhibits this stimulation in both the variant 3 and in the wild-type L1210 cells. The variant cells have a twofold higher than the wild-type cells. The (for NAD) and Kj (for 3-aminobenzamide) values are the same for both wild-type L1210 and variant 3 cell enz)mies (Kj 13.2 juM for SAB). 

Interestingly, substitution of the L-Arg residue in nodularin with L-Val (trivially named mutoporin) leads to biological properties which are somewhat different from those of other nodularins. This variant exerts cytotoxicity against tumour cell lines (49), a property not shown by nodularin. Derivatization of the Arg residue in nodularin with acetylacetone to produce the dimethylpyrimidyl-analog led to similar results as the new compound was found to be cytotoxic to L1210 cells (53). Probably this cytotoxicity is also exerted by the microcystin mutants with both the X and Y position occupied by hydrophobic residues. 

Fig. 3. DNA ligase I and II activity in wild-type L1210 cells (upper panel) and in variant (mutant) 3 Qower panel) cells. The ligases were separated on an hydroxylapatite column as described in [12]. Upper panel wild-type CQ h lo erpanel variant (mutant) 3 cells. DNA ligase activity, Oprotein concentration...

Non-toxic concentrations of SAB enhance the cytotoxicity of DMS for wild-type (wt) L1210 cells quite markedly. One of the variant clones isolated, variant 3, showed no such potentiation of cytotoxicity of DMS by SAB although its survival to DMS did not differ from wild-type L1210 cells. 

In conclusion, we have isolated a variant (mutant) from wild-t e L1210 cells which is insensitive to SAB potentiation of DMS cytotoxicity. This variant is independent confirmatory evidence of ADPRT involvement in DNA repair and indicates that 3-aminobenzamide sensitivity is related to DNA Ugase activity. 

Nudka N, Shall S (1980) 5-Methylnicotinamide resistant variant of mouse lymphoma L1210 cells. Biochem Biophys Res Commun 96 997-1002... 

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