Identification of piRNAs in heLa cells by massive parallel sequencing

Abstract

Piwi proteins and Piwi-interacting RNAs (piRNAs) have been implicated in transposon control in germ line from Drosophila to mammals. To examine the profi le of small RNA transcriptome and explore the potential roles of Human Piwilike 2 gene (alias HILI) and its associated piRNAs in human cancer cells, small RNA libraries prepared from HILI-overexpressed, HILI-knockdown, and control HeLa cells were respectively sequenced using Solexa, a next-generation massive parallel sequencing technology. A set of piRNAs and other repeat- associated small RNAs were observed in HeLa cells. By using in situ hybridization, piR-49322 was localized in the nucleolus and around the periphery of nuclear membrane in HeLa cells. Following the overexpression of HILI, the retrotransposon element LINE1 was significantly repressed, while LINE1-associated small RNAs decreased in abundance. The present study demonstrated that HILI along with piRNAs plays a role in LINE1 suppression in HeLa cancer cell line.