Characterization of the piRNA Complex from Rat Testes

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Science  21 Jul 2006:
Vol. 313, Issue 5785, pp. 363-367
DOI: 10.1126/science.1130164

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Small noncoding RNAs regulate processes essential for cell growth and development, including mRNA degradation, translational repression, and transcriptional gene silencing (TGS). During a search for candidate mammalian factors for TGS, we purified a complex that contains small RNAs and Riwi, the rat homolog to human Piwi. The RNAs, frequently 29 to 30 nucleotides in length, are called Piwi-interacting RNAs (piRNAs), 94% of which map to 100 defined (≤101 kb) genomic regions. Within these regions, the piRNAs generally distribute across only one genomic strand or distribute on two strands but in a divergent, nonoverlapping manner. Preparations of piRNA complex (piRC) contain rRecQ1, which is homologous to qde-3 from Neurospora, a gene implicated in silencing pathways. Piwi has been genetically linked to TGS in flies, and slicer activity cofractionates with the purified complex. These results are consistent with a gene-silencing role for piRC in mammals.

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