Selective ligation of DNA molecules following microinjection

Avian retroviral DNA is rapidly ligated and transcribed following microinjection into chick cells. To analyze the fidelity of intranuclear ligations, DNA molecules with a variety of protruding ends or flush ends were co-injected into env-deficient Rous sarcoma virus-infected (RSV(-] cells. Two fragments were chosen which could complement the RSV(-) env deficiency upon ligation. This sensitive biological assay indicated that intracellular ligation between molecules with complementary protruding ends or flush ends was relatively efficient. Ligation was not observed with non-complementary termini. Furthermore, when multiple DNA molecules possessing a variety of protruding termini were introduced into the cells, complementary termini were selectively joined. Finally, when viral DNAs which expressed separate genetic markers were co-injected, almost 50% of the virus subsequently released were recombinants, indicating that ligations generally involved multiple molecules.