Retention of tumour-inducing capacity by adenovirus DNA after cleavage by restriction endonucleases.

Abstract

WE have previously reported that fragments of Simian adenovirus SA7 DNA produced by physical breakage are oncogenic1. These fragments had an average molecular weight corresponding to half-molecules (11.4× 106). After separation of the heavy and light molecular halves by density gradient centrifugation, we demonstrated that both half-molecule preparations retain the ability to initiate tumours in newborn hamsters. We suggested that this may be caused by the presence of one or more “oncogenic regions” in both molecular halves, or by random breaks near the centre of the DNA which could result in a single small oncogenic region, residing near the centre and occurring with equal probability in either the heavy or light half-molecule preparation. To clarify these results we have studied the effect of several restriction endonucleases on the oncogenic activity of SA7 DNA. These enzymes produce defined fragments of the SA7 genome rather than the heterogeneous populations produced by physical shear.