Studies on the mechanism of replication of adenovirus DNA

Abstract

ReplicatingAd5 DNA was isolated from nuclei of infected KB cells and studied by electron microscopy. Branched as well as unbranched linear intermediates were observed containing extended regions of single-stranded DNA. The relationship between the branched and unbranched structures was studied during synchronized synthesis in the first round of replication after release of hydroxyurea inhibition.The branched intermediates represented early and the unbranched intermediates late stages in the replication cycle. Digestion of the branched intermediates with Eco RI endonuclease revealed that replication had started at the molecular right end (the A-T-rich end). This was confirmed by partial denaturation mapping of branched intermediates. These results confirm and extend a tentative model on the mechanism of Ad5 DNA replication.

An adenovirus type 5 gene function required for initiation of viral DNA replication

“…Based upon electron microscopical data, we have put forward the hypothesis that DNA replication starts at the right molecular end, copying the parental L-strand and at the same time displacing the H-strand. This so-called displacement synthesis leads to replicating intermediates containing a single-stranded H-strand, since the conversion of the Hstrand to a duplex (called complementarystrand synthesis) is considerably delayed Ellens et al, 1974). Initiation of displacement synthesis apparently requires the H5ts125 gene product, but we have no evidence for a similar involvement of this protein in the initiation of the complementary-strand synthesis.…”

The nucleotide sequence of the right-hand terminus of adenovirus type 5 DNA: Implications for the mechanism of DNA replication

“…Electron microscopical analysis of partially denatured Ad5 DNA has shown that the terminal 3% of the genome exhibits high denaturability, indicating a relatively high A+T content in this region (Ellens et al, 1974). This observation is confirmed by the sequence data, the overall A+T content being about 55%.…”

Electron Microscopy of Herpes Simplex Virus DNA Molecules Isolated from Infected Cells by Centrifugation in CsCl Density Gradients

“…Bidirectional semi-conservative replication initiated at these positions could lead to the formation of the replicative loops and Y-shaped molecules described in this study. The third predicted initiation site at one of the ends of the HSV DNA molecule could lead to the formation of HSV DNA possibly by strand displacement as described for adenovirus DNA replication (Ellens et al 1974). Models demonstrating three possible modes of replication for the eight molecular forms of HSV DNA shown in Fig.…”