Non-conserved proteins of human herpesvirus-8: Their possible roles in viral biology and pathogenesis

Determinations of the complete genomic sequences of eight herpesviruses of the gamma subfamily has enabled appreciation of the patterns of genetic divergence, with respect to gene content, organisation and encoded protein sequences, and the recognition of genes likely to contribute to biological properties that define the subfamily or that contribute to particular characteristics of individual viruses. Thus, genes that are unique, found only in some gammaherpesviruses or highly divergent between different gammaherpesviruses are candidates for determinants of virus-specific (non-universal) properties. Genes specific to and conserved amongst the gammaherpesviruses presumably contribute to the general characteristics of the subfamily. With regard to the former category, HHV-8 provides an especially rich collection of such genes, some of them with identifiable cellular homologues, that are unique to the virus, conserved only in a subset of its fellow gamma-2 herpesviruses, or that encode products with amino acid sequences that are highly diverged from their counterparts in other gamma-herpesviruses. These genes include those that specify functions associated with signal transduction, immune evasion and cellular proliferation and survival. The potential roles of these genes in viral biology and pathogenesis are the subject of this review.