Biological Funtions of piRNA

The non-coding RNAs(ncRNAs) has three major families,siRNA(small interfering RNA),miRNA(microRNA) and piRNA(piwi-interacting RNA).The piRNAs bind specifically to the piwi proteins of the Argonaute familys,and functioned in the maintainance of germline DNA integrity,silencing of transposon transcription,translation suppression,heterochromatin formation,epigenetic regulation and gametogenesis.The piRNA-coding sequences are often located discontinuously throughout the genome in clusters of 20～90 kb.Different from the siRNAs or miRNAs,which are derived from double-stranded or short-hairpin RNA precursors,piRNAs are derived from single-stranded RNA precursors or two non-overlapping and divergently transcribed precursors without the involvement of Dicer endonucleases.As a class of small riboregulators,piRNA was originated since the dawn of animal evolution.It might have promoted the formation of multi cellular animal species and contributed to the current complexities and diversities of life forms.This review intends to introduce the latest results related to the mechanisms of formation and functions of piRNAs.