Advanced methods for the manipulation of herpesvirus genomes

: The Herpesviridae are a family of viruses which have a large genome of linear, double-stranded DNA (> 120 kb). It has been quite difficult to clone and modify herpesvirus genomes because of their large sizes. Recently, several groups of investigators demonstrated successful cloning of infectious herpesvirus genomes as bacterial artificial chromosomes (BACs). In this review, I describe the recent development of methods to modify the cloned viral genomes. The methods are: (i) homologous recombination in E. coli which allows targeted mutagenesis of any specific viral sequence, and (ii) mutagenesis which allows random modification of entire viral genomes. Both methods should facilitate both the study of herpes viruses and the development of herpesvirus-based vector system.