Acipenser iridovirus-European encodes a replication factor C (RFC) sub-unit
New genomic sequence data were acquired for the Acipenser iridovirus-European (AcIV-E), a virus whose complete genome and classification still remain to be elucidated. Here, we obtained the first full-length Major capsid protein (MCP) gene sequence for AcIV-E, as well as two additional open reading frames (ORFs) adjacent to the MCP gene. BLAST searches of the first ORF (α) resulted in no match to any gene or protein in the public databases. The other ORF (β) was identified as a subunit of a replication factor C (RFC), known to function as a clamp loader in eukaryotes, archae and some viruses. The presence of similar RFC genes was confirmed in two distinct, yet related, viruses, the white sturgeon iridovirus and a European variant of Namao virus. The existence of an RFC gene in AcIV-E suggests a genome size larger than that of other classifiable members of the family Iridoviridae along with a mode of replication involving an interaction between a clamp loader and a proliferating nuclear cell antigen. Sequencing and comparison of the full-length RFC gene from various sturgeon samples infected with AcIV-E revealed two distinct clusters of sequences within one particular sample in which the coexistence of two lineages had previously been predicted based on analysis of the partial MCP gene sequence. These genetic data provide further evidence of the circulation of at least two concurrent AcIV-E lineages, sometimes co-infecting cultured European sturgeon.
Compliance with ethical standards
This study (ACIVIR2 project) was funded by the European Regional Development Fund (FEDER 160710), the Nouvelle Aquitaine regional council and partner fish farmers.
Conflict of interest
B Debeuf and V. Chesneau work for private companies cited in the authors’ list. The other authors declare that there are no competing interests regarding the publication of this paper.
The samples originated from moribund farmed fish, not submitted to experimentations and euthanized in accordance with animal welfare and ethics.
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