piRNAs in the germ line

Small noncoding RNAs have emerged as potent regulators of gene expression at both transcriptional and posttranscriptional levels. Recently, a class of small RNAs that interact with Piwi proteins has been discovered in the mammalian germ line and Drosophila. These Piwi-interacting RNAs (piRNAs) represent a distinct small RNA pathway.