Beyond's Dicer Cut

JAVIER PALATNIK

Nature Plants

Nature

Año: 2019

MicroRNAs (miRNAs) are only 20?24 nucleotides long but are essentialregulators of gene expression in plants and animals. With functions ranging from1✉118/10/2019 e.Proofinghttps://eproofing.springer.com/journals_v2/printpage.php?token=2cfkb0SgWaQMhGl0ZniBEaQdNyXaCVo6T3WTEx5_7tE2-KBOB0H-LQ 2/6the control of growth and development to hormone signalling and response tostress, these small RNAs are part of a plant?s daily life. miRNAs bind tocomplementary sequences in target RNAs and guide them to cleavage ortranslational arrest. However, to generate these short RNAs with specificsequences, plants need to turn on a complex machinery. MIRNA genes aretranscribed by RNA polymerase II into primary transcripts that display afoldback structure. The plant microprocessor cuts the primary transcript and, inmost cases, releases a stem-loop precursor, namely the pre-miRNA. A further cutto the pre-miRNA by the microprocessor generates a small RNA duplexharbouring the mature miRNA. Until now, plant pre-miRNAs were considered apassive intermediate step waiting for the next cut. However, in this issue ofNature Plants, Song et al.[1] demonstrate that plant pre-miRNAs are subject toextensive non-templated nucleotide additions consisting of cytidylation anduridylation at their 3? end (Fig. 1), revealing an extra layer of complexity to the miRNA biogenesis pathway