THE GENE ENCODING THE LATE NONSTRUCTURAL 36K PROTEIN OF VACCINIA VIRUS IS ESSENTIAL FOR VIRUS REPRODUCTION

Two genetic markers - the thymidine kinase gene of herpes simplex viru s, and the beta-galactosidase gene of Escherichia coli - were incorpor ated into the 36K protein gene (IL1 gene according to the nomenclature of the Copenhagen strain of vaccinia virus; Goebel et al., 1990) from the HindIII-P DNA fragment of the LIVP strain (variant of Lister stra in) of vaccinia virus (VV). After recombination of the obtained integr ation plasmid pVZ64-TK with the VV genome (tk-), it was found that the resultant TK+ viruses were unstable with respect to the Lac+ phenotyp e. On the basis of hybridization of DNA fragments of selected clones, a scheme for the formation of hybrid viruses is proposed, and an appro ach to a simple phenotypical discrimination between essential and non- essential genes for VV viability is described.