Putative nuclease that seems to be required for double-strand break repair, homologous recombination, and production of full-length viral genomic DNA. Binds 2 magnesium ions per subunit. They probably participate in the reaction catalyzed by the enzyme. Present in the virion core. Expressed in the early phase of the viral replicative cycle. When G5 is deleted, most of the DNA made in infected cells is not packaged in virus particles. Belongs to the XPG/RAD2 endonuclease family. FEN1 subfamily.