MicroRNAs are important biomolecules for regulating biological processes. Moreover, the secondary structure of microRNA is important for its activity and has been used previously as a mean for finding unknown microRNAs. A phylogenetic study of the microRNA secondary structure reveals more information than its primary sequence, because the primary sequence can undergo mutations that give rise to different phylogenetic relationships, whereas the secondary structure is more robust against mutations and therefore sometimes more informative.
Here we constructed a phylogenetic tree entirely based on microRNA secondary structures using tools PHYLIP (Felsenstein, 1995) and RNAforester (Matthias Höchsmann, 2003, Hochsmann et al., 2004), and compared the overall topology and clusters with the phylogenetic tree constructed using microRNA sequence. The purpose behind this comparison was to investigate the sequence and structure similarity in phylogenetic context and also to investigate if functionally similar microRNA genes are closer in their structure-derived phylogenetic tree.
Our phylogenetic comparison shows that the sequence similarity has hardly any effect on the structure similarity in the phylogenetic tree. MicroRNAs that have similar function are closer in the phylogenetic tree based on secondary structure than its respective sequence phylogeny. Hence, this approach can be very useful in predicting the functions of the new microRNAs whose function is yet to be known, since the function of the miRNAs heavily relies on its secondary structure.