Structure of simian virus 40 DNA replicated by herpes simplex virus type 1

Replicating herpes simplex virus type 1 (HSV-1) DNA is known to form large branched structures. The aim of this study was to define whether HSV-l-spec ific DNA elements in cis play a critical role in formation of this structur e. We did this by investigating the structure of heterologous simian virus 40 (SV40) DNA, which is replicated in HSV-infected cells by SV40 large T-an tigen and defined HSV-encoded replication factors (e.g., DNA polymerase, si ngle-stranded DNA-binding protein, and helicase-primase). During this proce ss, extrachromosomal concatemeric DNA replication products are formed, indi cating a herpesvirus-specific replication mode. In this study, we found tha t the replicating SV40 DNA consisted of a complex branched structure indist inguishable from that of replicating HSV DNA. Thus, no HSV-specific DNA ele ment is necessary in cis for the formation of the large branched structure during HSV DNA replication. The trans-acting HSV DNA replication proteins s eem to be sufficient to generate these complex structures. Moreover, replic ating SV40 DNA showed a high frequency of homologous recombination events, which is typical for HSV DNA replication. However, in contrast to HSV origi n-bearing amplicon plasmids, SV40 plasmids bearing the HSV cleavage-packagi ng signal were not efficiently processed to linear 150-kb DNA packaged into HSV capsids. This indicates that initiation of DNA synthesis on HSV-ori de termines some, yet undefined, property of replicating HSV DNA, which is cru cial for regular processing of the replication intermediates to daughter ge nomes. (C) 2000 Academic Press.