CLONING, SEQUENCE-ANALYSIS, AND EXPRESSION OF THE MAJOR CAPSID PROTEIN OF THE IRIDOVIRUS FROG VIRUS-3

The nucleotide sequence of the gene encoding the major capsid protein (MCP) of frog virus 3 (FV3) has been determined and compared to other iridovirus capsid genes. Nucleotide sequence and S1 nuclease analysis showed that the FV3 MCP gene encoded a transcript of 1452 nucleotides containing a 12 nucleotide AU-rich 5' nontranslated region (NTR) and a 50-nucleotide 3' NTR whose terminus was predicted to fold into a hair pin of moderate stability. An open reading frame initiating from the 5 '-most AUG codon encoded a protein of 463 amino acids with a predicted molecular weight of 49,860. Expression of the putative FV3 MCP gene i n vitro confirmed that it encoded the major capsid protein of FV3 and supported the suggestion that translation initiated at AUG-1. Pairwise amino acid alignments detected a high degree of sequence identity bet ween the FV3 MCP and other iridoviruses. These results indicate that i ridoviruses possess an evolutionarily related major capsid protein and provide information useful not only in studies of viral gene expressi on, but also in characterizing newly isolated iridoviruses. (C) 1996 A cademic Press, Inc.