PDF(Sci-hub)
Abstract：
In animal gonads, PIWI-clade Argonaute proteins repress transposons sequence-specifically via bound Piwi-interacting RNAs (piRNAs). These are processed from single-stranded precursor RNAs by largely unknown mechanisms. Here we show that primary piRNA biogenesis is a 3\'-directed and phased process that, in the Drosophila germ line, is initiated by secondary piRNA-guided transcript cleavage. Phasing results from consecutive endonucleolytic cleavages catalyzed by Zucchini, implying coupled formation of 3\' and 5\' ends of flanking piRNAs. Unexpectedly, Zucchini also participates in 3\' end formation of secondary piRNAs. Its function can, however, be bypassed by downstream piRNA-guided precursor cleavages coupled to exonucleolytic trimming. Our data uncover an evolutionarily conserved piRNA biogenesis mechanism in which Zucchini plays a central role in defining piRNA 5\' and 3\' ends.
摘要：
在动物性腺中，PIWI进化枝Argonaute蛋白通过结合的Piwi相互作用RNA（piRNA）序列特异性抑制转座子。这些是通过大部分未知的机制从单链前体RNA加工的。在这里，我们表明初级piRNA生物发生是一个3'-定向和分阶段的过程，在果蝇种系中，由第二次piRNA引导的转录物切割起始。西葫芦催化的连续核酸内切裂解的定相结果，暗示侧翼piRNAs的3'和5'末端的偶联形成。出乎意料的是,西葫芦还参与次级piRNAs的3'端形成。它的功能可以，然而,通过与核酸外切修剪偶联的下游piRNA引导的前体切割来绕过。我们的数据揭示了进化上保守的piRNA生物发生机制，其中西葫芦在定义piRNA5'和3'末端中起着核心作用。
