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Herpesviridae is a family of enveloped, doublestranded DNA viruses with relatively large complex genomes. They have a wide range of vertebrate hosts, including eight varieties isolated in human, several each in horses, cattle, mice, pigs, chickens, turtles, lizards, fish, and even in some invertebrates, such as oysters (1, 3). The origins of herpesviruses are the subject of interesting but largely unverifiable speculations. The presence of homologs in many viruses indicates that herpesviruses acquired many of their genes from a common ancestral virus or cellular genomes.
The proteins encoded by β-gene including UL2 and UL23 are expressed after the activation of immediateearly proteins (14, 15, 16). They play a critical role in replication stage of DNA. Since all viruses are parasitic to cellular organisms and require molecular machinery produced by their cellular hosts in order to complete their life cycles (4, 5, 7), a homology analysis on the protein conserved among the herpesviruses could provide some clarification of the replication pattern of HSV. Very few papers describe the evolution of early proteins in these pathogens, and the aim of this study is to align selected gene sequences of several early proteins and to perform phylogenetic studies to further clarify the properties of these pathogens.
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We used BlastP with an E-value of 10-20 to search all predicted proteins from the set of Herpesvirus or non-virus genomes against the following sequences of HSV1: complete protein translations (proteome) for UL2 and UL23. The GenBank accession numbers of the protein sequences derived in this study are listed in Table 1. Phylogenetic trees were constructed for each protein family present in all species of Herpesvirus analyzed.
Table 1. The GenBank accession numbers of the protein sequences enrolled
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The sequence data were aligned using MEGA package (version 3.1) (10), and phylogenetic trees were constructed using the neighbor-joining program, from a distance matrix corrected for nucleotide substitutions by the Kimura two-parameter model. Tree stability was assessed via bootstrapping over 500 replicates and if the bootstrap value exceeded 95%, then the cluster was regarded as strongly supported.