Abstract
BackgroundTiger frog virus (TFV), dsDNA virus of the genus Ranavirus and family Iridoviridae, causes a high mortality of tiger frog tadpoles cultured in Southern China. MicroRNAs (miRNAs) have been identified in many viruses especially DNA viruses such as Singapore Grouper Iridoviruses (SGIV). MicroRNAs play important roles in regulating gene expression for virus subsistence in host. Considering that TFV infects cells of different species under laboratory conditions, we aim to identify the specific and essential miRNAs expressed in ZF4 and HepG2 cells.MethodsWe identified and predicted novel viral miRNAs in TFV-infected ZF4 and HepG2 cells by deep sequencing and software prediction. Then, we verified and described the expression patterns of TFV-encoded miRNAs by using qRT-PCR and Northern blot.ResultsDeep sequencing predicted 24 novel TFV-encoded miRNAs, and qRT-PCR verified 19 and 23 miRNAs in TFV-infected ZF4 (Group Z) and HepG2 (Group H) cells, respectively. Northern blot was performed to validate eight and five TFV-encoded miRNAs in Groups H and Z, respectively. We compared the expression of TFV-encoded miRNAs from two groups and defined TFV-miR-11 as the essential viral miRNA and TFV-miR-13 and TFV-miR-14 as the specific miRNAs that contribute to HepG2 cell infection.ConclusionsWe identified novel viral miRNAs and compared their expression in two host cells. The results of this study provide novel insights into the role of viral miRNAs in cross-species infection in vitro.Electronic supplementary materialThe online version of this article (doi:10.1186/s12985-016-0530-6) contains supplementary material, which is available to authorized users.
Highlights
Tiger frog virus (TFV), dsDNA virus of the genus Ranavirus and family Iridoviridae, causes a high mortality of tiger frog tadpoles cultured in Southern China
We identified novel viral miRNAs encoded by TFV and analyzed the diversity of miRNA expression in fish (ZF4) and mammalian (HepG2) cells to define the essential and specific miRNAs in crossspecies in vitro
Deep sequencing of small RNAs from ZF4 and HepG2 cells infected by TFV From the deep sequencing raw data of small RNAs derived from HepG2 (Group H) and ZF4 (Group Z) cells infected with TFV, we obtained 22,095,484 reads from Group H, including 22,030,626 high-quality reads, and 26,116,906 reads from Group Z, including 25,952,342 high-quality reads
Summary
Tiger frog virus (TFV), dsDNA virus of the genus Ranavirus and family Iridoviridae, causes a high mortality of tiger frog tadpoles cultured in Southern China. MicroRNAs play important roles in regulating gene expression for virus subsistence in host. Mature miRNAs are noncoding RNAs approximately 21 to 22 nucleotides long [6] that regulate cellular processes such as immunity, apoptosis, development and other important aspects, The first virus-encoded miRNAs were identified from Epstein–Barr virus (EBV) in 2004 [8]. Several virus-encoded miRNAs have been found in different DNA viruses [9], including members of the Herpesviridae, Polyomaviridae, Ascoviridae, Baculoviridae, Iridoviridae and Adenoviridae families [10], and in a lone RNA virus, bovine leukemia virus [11]. Some virus-encoded miRNAs mimic host miRNAs and regulate the host transcripts to help the virus stay in the host [13]. MiRBART5 encoded by EBV inhibits the protein p53 upregulated modulator of apoptosis (PUMA) to prevent
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