Studies in AMV DNA. I. Physical properties and sequence composition of DNA present in AMV virions (AMV DNA)

The basic physical properties of AMV DNA (labeled with 3H-thymidine) as well as sequence homology between 3H-AMV DNA and viral or host cell genomes were investigated. It was found that native AMV DNA is in part single-stranded (20% of the total DNA). Using CsCl density gradient centrifugation AMV DNA was separated into two bands with buoyant densities of 1.702 g/cm3 (L-AMV DNA) and 1.722 g/cm3 (H-AMV DNA) in the peak fractions. Corresponding melting temperatures were estimated to be 82.0 degrees C and 81.3 degrees C for L- and H-AMV DNA, respectively. Hybridization experiments revealed that AMV DNA is not complementary to the AMV genomic RNA but complementary prevalently to the sequences with low frequency of repetition and to the unique sequences of the myeloblast genome. These unique sequences, comprising about 40% of the total 3H-AMV DNA, were not detected in the nuclear DNA of leukosis-free chicken embryo fibroblasts. After infection of embryo cells with AMV the extent of hybridization in the region of unique sequences rose roughly by 20%. Renaturation of thermally denatured 3H-AMV DNA using the phenol emulsion reassociation technique was observed. The results suggest that AMV DNA is composed of a number of different special sequences of the host genome.