Hollings Marine Laboratory, National Institute of Standards and Technology, 331 Fort Johnson Rd., Charleston, SC 29412, USA.
J Virol. 2011 Dec;85(24):13398-408. doi: 10.1128/JVI.06250-11. Epub 2011 Oct 12.
Infectious salmon anemia virus (ISAV) has emerged as a virus of great concern to the aquaculture industry since it can lead to highly contagious and lethal infections in farm-raised salmon populations. While little is known about the transcription/replication cycle of ISAV, initial evidence suggests that it follows molecular mechanisms similar to those found in other orthomyxoviruses, which include the highly pathogenic influenza A (inf A) virus. During the life cycle of orthomyxoviruses, a panhandle structure is formed by the pairing of the conserved 5' and 3' ends of each genomic RNA. This structural motif serves both as a promoter of the viral RNA (vRNA)-dependent RNA polymerase and as a regulatory element in the transcription/replication cycle. As a first step toward characterizing the structure of the ISAV panhandle, here we have determined the secondary structures of the vRNA and the cRNA panhandles on the basis of solution nuclear magnetic resonance (NMR) and thermal melting data. The vRNA panhandle is distinguished by three noncanonical U · G pairs and one U · U pair in two stem helices that are linked by a highly stacked internal loop. For the cRNA panhandle, a contiguous stem helix with a protonated C · A pair near the terminus and tandem downstream U · U pairs was found. The observed noncanonical base pairs and base stacking features of the ISAV RNA panhandle motif provide the first insight into structural features that may govern recognition by the viral RNA polymerase.
传染性鲑鱼贫血病毒（ISAV）是一种对水产养殖业非常关注的病毒，因为它可导致养殖鲑鱼种群中高度传染性和致命性感染。尽管人们对 ISAV 的转录/复制周期知之甚少，但初步证据表明，它遵循与其他正粘病毒（包括高致病性甲型流感（inf A）病毒）相似的分子机制。在正粘病毒的生命周期中，每个基因组 RNA 的保守 5' 和 3' 末端配对形成一个“柄状结构”。该结构基序既是病毒 RNA（vRNA）依赖性 RNA 聚合酶的启动子，也是转录/复制周期中的调节元件。为了表征 ISAV 柄状结构的结构，我们根据溶液核磁共振（NMR）和热融解数据确定了 vRNA 和 cRNA 柄状结构的二级结构。vRNA 柄状结构通过两个茎环中的三个非典型 U · G 对和一个 U · U 对来区分，这两个茎环由一个高度堆积的内部环连接。对于 cRNA 柄状结构，发现了一个连续的茎环，其末端附近有一个质子化的 C · A 对，下游有串联的 U · U 对。ISAV RNA 柄状结构基序中观察到的非典型碱基对和碱基堆积特征为可能控制病毒 RNA 聚合酶识别的结构特征提供了第一个见解。
