[Characteristics of the effect of Ca/Mg-dependent endonuclease from cell nuclei of human lymphocytes on J kappa-cluster of immunoglobulin genes].

The cleavage of the murine J kappa-segments by purified Ca/Mg-dependent endonuclease was studied. The enzyme was shown to cleave specifically the J kappa-segments introducing the double strand breaks in 5'-regions of the J kappa-genes. The number of thus generated discreet fragments does not change during incubation. Specificity of the enzyme is not changed by substitution of Ca/Mg for Mn. The enzyme activity is inhibited by 0.1 M NaCl as well as its specificity. Comparison of the enzyme with the known nuclease activities that cleave specifically the J kappa-segments demonstrated that the activities of the latter are determined by Ca/Mg-dependent endonuclease. The results suggest the possible participation of Ca/Mg-dependent endonuclease in Ig-genes recombination.