T4 DNA-LIGASE MODULATES CHROMOSOME-DAMAGE INDUCED BY RESTRICTION ENDONUCLEASES THROUGH AN ERROR-FREE PROCESS

The possible modulation by T4 DNA ligase of the DNA double-strand brea ks produced by restriction endonucleases in living mammalian cells was studied. A clear decrease in the frequency of chromosomal aberrations was observed when T4 DNA ligase was included in the electroporation t reatment along with restriction enzymes inducing either cohesive- or b lunt-ends in DNA. The relative proportions of exchange-type aberration s were similar for both kinds of treatments (with and without ligase), which seems to suggest an error-free ligation by T4 DNA ligase.