miRNAs encode miPEPs

Sci. Signal.  07 Apr 2015:
Vol. 8, Issue 371, pp. ec83
DOI: 10.1126/scisignal.aab2754

Noncoding RNAs (ncRNAs), including microRNAs (miRNAs), have the potential to encode proteins. miRNAs are transcribed as larger primary transcripts called the primary miRNA (pri-miRNA), which are later processed to form the active miRNAs that regulate a specific set of target genes. Using bioinformatics analysis, Lauressergues et al. found that two plant pri-miRNAs, pri-miR171b from Medicago truncatula and pri-miR165a from Arabidopsis thaliana, had short open reading frames that could potentially code for peptides. To investigate whether the two start codons of the putative open reading frames (ORFs) in the pri-miR171b are active, the authors fused beta-glucuronidase reporter gene encoding GUS to the promoter regions of the respective ORFs and showed that one functioned as an ORF, inducing production of GUS. An antibody generated against the peptide encoded by ORF1 of M. truncatula detected miPEP-171b by immunofluorescence microscopy in initiating lateral roots. Mutation of the start codon reduced the abundance of the pri-miRNA and the mature miRNA in roots, indicating a functional role for this peptide in stabilizing the pri-miRNA. Putative ORFs are present in five other pri-miRNAs of A. thaliana and M. truncatula, suggesting that miPEPs may be common in plants (see Waterhouse and Hellens). Future studies will reveal if these are also common in animals.

D. Lauressergues, J.-M. Couzigou, H. San Clemente, Y. Martinez, C. Dunand, G. Bécard, J.-P. Combier, Primary transcripts of microRNAs encode regulatory peptides. Nature 520, 90–93 (2015). [PubMed]

P. M. Waterhouse, R. P. Hellens, Coding in non-coding RNAs. Nature 520, 41–42 (2015) [PubMed]