Variation in DNA ligase structure during repair and replication processes in monkey kidney cells.

Using a method that detects catalytically active DNA ligase in NaDodSO4-polyacrylamide gels (activity gels) we have characterized ligase produced in CV1-P monkey kidney cells infected with SV40 or treated with mitomycin C. Purification on hydroxylapatite columns of DNA ligase from control cells results in two peaks of activity called ligases I and II, respectively. Analysis of ligase I on activity gels revealed major catalytic peptides with Mr of 120, 110, 70 and 58 kDa, while analysis of ligase II revealed two major peptides of 65 and 58 kDa. Infecting CV1-P cells with SV40 produced a significant increase in the 120, 110, 70 and 58 kDa peptides while treating them with mitomycin C produced a significant increase in the 70 and 58 kDa peptides and a decrease in the 120 and 110 kDa ones. Autoproteolysis of partially purified ligase under several conditions resulted in an increase in the 58 kDa peptide and in the disappearance of other peptides. These results suggest that at least one active polypeptide is common to ligases I and II.