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piRNA-guided slicing of transposon transcripts enforces their transcriptional
silencing via specifying the nuclear piRNA repertoire
#MMPMID26302790
Senti KA
; Jurczak D
; Sachidanandam R
; Brennecke J
Genes Dev
2015[Aug]; 29
(16
): 1747-62
PMID26302790
show ga
PIWI clade Argonaute proteins silence transposon expression in animal gonads.
Their target specificity is defined by bound ?23- to 30-nucleotide (nt)
PIWI-interacting RNAs (piRNAs) that are processed from single-stranded precursor
transcripts via two distinct pathways. Primary piRNAs are defined by the
endonuclease Zucchini, while biogenesis of secondary piRNAs depends on
piRNA-guided transcript cleavage and results in piRNA amplification. Here, we
analyze the interdependencies between these piRNA biogenesis pathways in
developing Drosophila ovaries. We show that secondary piRNA-guided target slicing
is the predominant mechanism that specifies transcripts?including those from
piRNA clusters?as primary piRNA precursors and defines the spectrum of Piwi-bound
piRNAs in germline cells. Post-transcriptional silencing in the cytoplasm
therefore enforces nuclear transcriptional target silencing, which ensures the
tight suppression of transposons during oogenesis. As target slicing also defines
the nuclear piRNA pool during mouse spermatogenesis, our findings uncover an
unexpected conceptual similarity between the mouse and fly piRNA pathways.
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