Mammalian microRNAs derived from genomic repeats

Area of Science:

• Genomics
• Molecular Biology
• Evolutionary Biology

Background:

• MicroRNAs (miRNAs) are key regulators of gene expression in mammals.
• The origins of novel miRNAs, particularly those arising during evolution, are not fully understood.
• Transposable elements (TEs) are mobile DNA sequences that can alter genome structure and function.

Purpose of the Study:

• To investigate the origin of a subset of mammalian microRNAs.
• To determine if genomic repeats contribute to miRNA biogenesis.
• To explore the role of transposable elements in the generation of new miRNAs during mammalian evolution.

Main Methods:

• Bioinformatic analysis of mammalian genomes to identify miRNA precursors.
• Comparative genomics to trace the evolutionary history of repeat-derived miRNAs.
• RNA sequencing and expression analysis to characterize novel miRNAs and their targets.

Main Results:

• A subset of conventional mammalian microRNAs is derived from LINE-2 transposable elements and other genomic repeats.
• These repeat-derived miRNAs originate from standard hairpin precursors, differing from rasiRNAs.
• Transposable element insertions are identified as a significant driver for the creation of new miRNAs in mammalian evolution.
• Two specific LINE-2-derived miRNAs show perfect complementarity to numerous mRNA and EST transcripts containing MIR and LINE-2 elements.

Conclusions:

• Genomic repeats, particularly LINE-2 elements, are a source of novel mammalian microRNAs.
• Transposable element activity plays a crucial role in miRNA innovation and evolution.
• Repeat-derived miRNAs can regulate gene expression by targeting transcripts with complementary sequences in their 3'-untranslated regions.