piRNA biogenesis during adult spermatogenesis in mice is independent of the ping-pong mechanism
piRNA biogenesis during adult spermatogenesis in mice is independent of the ping-pong mechanism
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DOI：
10.1038/cr.2012.120
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发表时间：
2012-10-01
期刊：
影响因子：
44.1
通讯作者：
Lin, Haifan
中科院分区：
文献类型：
--
作者：
Beyret, Ergin;Liu, Na;Lin, Haifan
piRNA是一类与PIWI蛋白相关的小的非编码RNA，在种系发育、转座子沉默和表观遗传调控中具有广泛的功能。在不同的生物体中，衍生自重复序列的piRNA的子集通过两种PIWI蛋白之间的相互作用产生。这种机制，被称为“乒乓”循环，在原始小鼠睾丸的PIWI蛋白之间运作;然而，它在出生后睾丸中的参与仍然难以捉摸。在这里，我们表明，成年睾丸piRNA的产生独立于乒乓机制。我们鉴定并表征了与MILI和MIWI相关的成年和出生后发育中的睾丸中的大量piRNA，这是在这些睾丸中可检测到的唯一PIWI蛋白。在成年睾丸中未检测到MILI和MIWI之间的相互作用或其piRNA之间的乒乓机制的序列特征。大多数MILI和MIWI相关的piRNA源自相同基因座内的相同DNA链。两个piRNA群体在第10个核苷酸位置上偏向于5'尿嘧啶，但不偏向于腺嘌呤，并且不显示互补性。此外，在Miwi突变体中，MILI相关的piRNA没有下调，而是上调。这些结果表明，成年睾丸piRNA主要（如果不是唯一的话）由初级加工机制而不是乒乓机制产生。在该主要途径中，MILI和MIWI相关的piRNA的生物发生可能竞争相同的前体;所产生的piRNA的类型往往由细胞中可用的前体非选择性地决定;并且具有内含子的前体往往在加工成piRNA之前被剪接。
piRNAs, a class of small non-coding RNAs associated with PIWI proteins, have broad functions in germline development, transposon silencing, and epigenetic regulation. In diverse organisms, a subset of piRNAs derived from repeat sequences are produced via the interplay between two PIWI proteins. This mechanism, termed "ping-pong" cycle, operates among the PIWI proteins of the primordial mouse testis; however, its involvement in postnatal testes remains elusive. Here we show that adult testicular piRNAs are produced independent of the ping-pong mechanism. We identified and characterized large populations of piRNAs in the adult and postnatal developing testes associated with MILI and MIWI, the only PIWI proteins detectable in these testes. No interaction between MILI and MIWI or sequence feature for the ping-pong mechanism among their piRNAs was detected in the adult testis. The majority of MILI- and MIWI-associated piRNAs originate from the same DNA strands within the same loci. Both populations of piRNAs are biased for 5' Uracil but not for Adenine on the 10th nucleotide position, and display no complementarity. Furthermore, in Miwi mutants, MILI-associated piRNAs are not downregulated, but instead upregulated. These results indicate that the adult testicular piRNAs are predominantly, if not exclusively, produced by a primary processing mechanism instead of the ping-pong mechanism. In this primary pathway, biogenesis of MILI-and MIWI-associated piRNAs may compete for the same precursors; the types of piRNAs produced tend to be non-selectively dictated by the available precursors in the cell; and precursors with introns tend to be spliced before processed into piRNAs.