The Evolution of Virus-Encoded microRNAs in Herpesvirus Family
|摘要:||微型核糖核酸含有約二十到三十個核苷酸，它於 1993 年線蟲發育研究中被
MicroRNA (miRNA), a small RNA containing only twenty to thirty nucleotides, was discovered in a developmental study of Caenorhabditis elegans in 1993. During the next decades, a lot of these small RNAs were found in many other organisms. By binding to their target messenger RNAs, miRNA could generate degradation or translational inhibition of their target sequences. The first viral miRNA was reported in 2004. Much research on the identification or function of miRNAs has been conducted in variety of viruses. One of these research findings is that viruses would use their miRNAs to regulate both viral and host gene expression. In this way, they could build a suitable environment and avoid the immune system in their hosts. Viral genes were proposed to originate from host genomes in previous phylogenetic studies of viruses. Hence, it is reasonable to speculate that viruses might obtain their miRNAs in the same way. To answer this question, I collected all viral miRNAs on the experimental verified miRNA database (miRBase) and compared the locations of these miRNAs in the viral genomes. I found that two closely related viruses could have similar genome contents, gene order, and even the location of cluster of miRNAs. However, the number and sequences of the miRNAs in the two clusters are completely different. Two hypotheses were therefore proposed. First, different viruses captured different miRNAs independently from their hosts while they employing their hosts' gene expression machinery. Alternatively, these miRNAs could be generated by accumulating enormous nucleotide substitutions after the two viruses were diverged from their common ancestor. To verify these two hypotheses, more miRNAs sequences, including predicted data, should be collected and analyzed. This study may give an insight into viral evolution in host-virus interaction.
|Appears in Collections:||Thesis|