Laboratoire Frank Duncombe, BioMEA-Université de Caen Basse-Normandie, Laboratoire Frank Duncombe, 14053 Caen Cedex 4, France.
Virus Res. 2013 Dec 26;178(2):462-70. doi: 10.1016/j.virusres.2013.08.006. Epub 2013 Sep 17.
The genetic polymorphism of the Ostreid Herpesvirus 1 (OsHV-1) has generally been investigated in three areas: ORFs 4/5, ORFs 42/43, and ORFs 35 to 38. The present study, however, focuses on 40 ORFs, representing 30% of the OsHV-1 genome, encoding four categories of putative proteins: 4 ORFs encoding putative inhibitor of apoptosis proteins; 17 ORFs encoding membrane proteins; 10 ORFs encoding secreted proteins; and 9 ORFs encoding RING finger proteins. The potential role of these proteins in major steps of the life cycle of the OsHV-1 motivated their selection. Seven specimens have been selected in accordance with their nucleotide variations in the C region (area located between the end of the ORF4 and the beginning of ORF 5): 3 OsHV-1μVar specimens, 2 OsHV-1μVar Δ9, one specimen of OsHV-1μVar Δ15, and one OsHV-1 specimen (reference control) close to the reference genome to validate PCRs. The OsHV-1μVar is mainly characterized by a deletion of 12 consecutive nucleotides followed by a deletion of one adenine in a microsatellite area located in the C region. A representation of nucleotide modifications between the different specimens was performed by building evolutionary trees with respect to the category of ORFs. This phylogenetic analysis revealed two groups: the first one corresponded to the reference control and the reference genome AY509253, and the second one included the 6 OsHV-1 variants. These results suggest that the two main groups come from the same common ancestor, and that the divergence between the reference OsHV-1 and its variants occurred quite far back in time. Moreover, consequences of nucleotide variations in the amino acid sequences, especially the change of the N glycoslyation sites, were investigated. Herein is the first report of four important deletions in these OsHV-1μVar variants: a deletion of 1385bp in ORF 11; a deletion of 599bp in ORF 48; a deletion of 3549bp in ORFs 61 to 64; and a deletion of 712bp in ORF 114. The size of the deletions differed between OsHV-1μVar specimens, OsHV-1μVar Δ9 specimens, and the OsHV-1μVar Δ15 specimen. These zones seem to correspond to special points of gene rearrangements for producing new proteins. Further investigation necessary proves to link such nucleotide modifications with consequences of protein functions in the OsHV-1 life cycle.
牡蛎疱疹病毒 1（OsHV-1）的遗传多态性通常在三个方面进行研究：ORFs 4/5、ORFs 42/43 和 ORFs 35 至 38。然而，本研究集中在 40 个 ORF 上，占 OsHV-1 基因组的 30%，编码四类假定的蛋白质：4 个 ORF 编码假定的凋亡抑制剂蛋白；17 个 ORF 编码膜蛋白；10 个 ORF 编码分泌蛋白；和 9 个 ORF 编码 RING 指蛋白。这些蛋白质在 OsHV-1 生命周期的主要步骤中的潜在作用促使它们被选择。根据 C 区（位于 ORF4 末端和 ORF5 起始之间的区域）的核苷酸变异选择了 7 个样本：3 个 OsHV-1μVar 样本、2 个 OsHV-1μVarΔ9、1 个 OsHV-1μVarΔ15 和 1 个 OsHV-1 样本（参考对照），以验证 PCR。OsHV-1μVar 主要特征是在 C 区微卫星区域中缺失 12 个连续核苷酸，随后缺失一个腺嘌呤。通过根据 ORF 类别构建进化树，对不同样本之间的核苷酸修饰进行了表示。该系统发育分析显示了两个组：第一个组对应于参考对照和参考基因组 AY509253，第二个组包括 6 个 OsHV-1 变体。这些结果表明，这两个主要组来自同一共同祖先，并且参考 OsHV-1 与其变体之间的分歧发生在很久以前。此外，还研究了核苷酸变异对氨基酸序列的影响，特别是 N 糖基化位点的变化。这是首次在这些 OsHV-1μVar 变体中报告了四个重要缺失：ORF11 中缺失 1385bp；ORF48 中缺失 599bp；ORFs61 至 64 中缺失 3549bp；ORF114 中缺失 712bp。OsHV-1μVar 样本、OsHV-1μVarΔ9 样本和 OsHV-1μVarΔ15 样本之间的缺失大小不同。这些区域似乎对应于产生新蛋白质的基因重排的特殊点。进一步的研究证明，这种核苷酸修饰与 OsHV-1 生命周期中蛋白质功能的后果有关。
