Identification of a gene cluster within the genome of Chilo iridescent virus encoding enzymes involved in viral DNA replication and processing

The nucleotide sequence of the genome of Chilo iridescent virus (CIV) betwe en the genome coordinates 0.974 and 0.101 comprising 27,079 bp was determin ed. Computer-assisted analysis of the DNA sequence of this particular regio n of the CIV genome revealed the presence of 42 potential open reading fram es (ORFs) with coding capacities for polypeptides ranging from 50 to 1,273 amino acid residues. The analysis of the amino acid sequences deduced from the individual ORFs resulted in the identification of 10 potential viral ge nes that show significant homology to functionally characterized proteins o f other species. A cluster of five viral genes that encode enzymes involved in the viral DNA replication was identified including the DNA topoisomeras e II (A039L, 1,132 amino acids (aa)), the DNA polymerase (ORF A031L, 1,273 aa), a helicase (ORF A027L, 530 aa), a nucleoside triphosphatase I (ORF A02 5L, 1,171 aa), and an exonuclease II (ORF A019L, 624 aa), all ORFs possessi ng the same genomic orientation. The DNA polymerase of CIV showed the highe st homology (24.8% identity) to the DNA polymerase of lymphocystis disease virus lymphocystis disease virus 1 (LCDV-1), a member of the family Iridovi ridae, indicating the close relatedness of the two viruses. In addition, fo ur putative gene products were found to be significantly homologous to prev iously identified hypothetical proteins of CIV.