Incomplete particles of adenovirus type 2 III. Viral and cellular DNA sequences in incomplete particles

Abstract

During the productive infection of human KB cells with adenovirus type 2, between 5 and 15% of the particles produced are incomplete and exhibit a buoyant density in CsCl density gradients which is 0.035–0.045 g × cm −3 lower than that of intact virions. Three density classes of incomplete particles are observed and have been designated la, 1b, and 2. The incomplete particles contain viral and cellular DNA. Viral DNA comprises only 2.8% of the DNA in incomplete particles. Reassociation kinetics experiments using each of the EcoRI fragments of adenovirus type 2 DNA indicate that all segments of the viral genome are represented and that the right end of the molecule occurs slightly more abundantly. The bulk of the DNA in incomplete particles is of cellular origin. In zonal sedimentation experiments with DNA from incomplete particles, two types of size distribution have been observed. In type 1, the DNA from incomplete particles sediments between 12.9 and 14 S; in type 2, there is a peak cosedimenting with the 31 S virion DNA used as marker and a broad peak between 5 and 25 S. The results of two-step filter hybridization experiments in which the 311-labeled DNA from incomplete particles was first annealed to Ad2 DNA on filters, then eluted, and subsequently hybridized with KB DNA on filters, suggest that some of the viral DNA from incomplete particles may be covalently linked to cellular DNA, but this problem requires further investigation.