The mouse homolog of HEN1 is a potential methylase for Piwi-interacting RNAs

Abstract

Piwi-interacting RNAs (piRNAs) are a novel class of small regulatory RNAs that are expressed specifically and abundantly in germ cells. Mammalian piRNAs are 26–31 nucleotides in length and bind to Piwi proteins, but their function and biogenesis remain elusive. We previously showed that mammalian piRNAs are 2′-O-methylated at their 3′ termini. The biosynthetic mechanism and function of this modification is unknown. Here, we report that the mouse homolog (mHEN1) of HEN1, a plant microRNA (miRNA) 2′-O-methyltransferase, is expressed specifically in testis and methylates 3′ termini of piRNAs in vitro. These findings provide insight into the biogenesis of piRNAs.