Viruses and long non-coding RNAs: implicating an evolutionary conserved region.

Long non-coding RNAs (lncRNAs) are a class of cellular transcripts, which are involved in various biological processes. There is conflicting data regarding to the origin of these non-coding molecules and lncRNAs are thought to be the origin of viral genome. Here we sought to find the homology between human lncRNAs and viruses. For this purpose, the lncRNAdb database was searched for human lncRNAs. The lncRNAs' sequences were aligned with virus taxa using NCBI's BLAST tool. The phylogenic study was performed with maximum-likelihood based algorithm. The database contains 152 human lncRNAs. As a result, 63 (41.44%) of the lncRNAs have homologies with viruses. Of which, 50 (79.36%) have homology with Stealth virus. Other viruses with homology to lncRNAs were nuclear integrating DNA/RNA viruses. Moreover, 35 of 64 (23.03%) of cancer-associated lncRNAs have sequence homology with the same viruses. In phylogenetic analyses, lncRNAs with no homology to viruses were found to be the ancestor of those with homology to viruses and cancer-irrelevant lncRNAs were found to be the ancestor of cancer-related transcripts. In conclusion, lncRNAs could be the origin of nuclear integrating viruses and the nuclear integrating viruses may evolved from the non-coding regions. The results imply the role of lncRNAs with homology to viruses in human cancers.