Abstract
BACKGROUND: In eukaryotic organisms, it has been well acknowledged that 3' untranslated regions (3' UTRs) of mRNA are actively involved in post-transcriptional regulations of gene expression. Although both shortening and lengthening of 3' UTRs of specific candidate genes were explicitly documented to have functional consequences, landscape of 3' UTR lengths in relation to evolutionary dynamics and biological meanings remains to be elucidated when large-scale data become available. OBJECTIVES: The primary objective of this study was to revealed different inter- and intra-species patterns on length distribution of 3' UTRs in comparison with 5' UTRs and coding regions. METHODS: In the present study, we investigated 3' UTR lengths in a highly curated set of 57,135 mRNA sequences among four well-studied and taxonomically diverse metazoan species (fruit fly, zebrafish, mouse and human). RESULTS: The average length ratio of 3'-5' UTRs considerably increased from fruit fly (twofold) to human (fivefold). Moreover, genes can be characterized by the obviously different patterns of evolutionary change on 3' UTR lengths. By utilizing the Gene Ontology annotations, genes with differential lengths of 3' UTRs were suggested to have the divergent functional implications. In human, we further revealed that ubiquitously transcribed genes had higher median lengths of 3' UTRs than the genes of tissue-restricted expressions. CONCLUSION: We conducted a comprehensive analysis and provided an overview regarding 3' UTRs biology of mRNAs in animals, whereas the mechanistic explanations of 3' UTRs length variation in correlation to regulation of gene expression still remain to be further studied.