TDRD5 binds piRNA precursors and selectively enhances pachytene piRNA processing in mice

Deqiang Ding,Uros Midic,Jiali Liu,Yingjie Wu,Kunzhe Dong,Chen Chen,Keith E Latham,Ashley Melnick

doi:10.1038/s41467-017-02622-w

Abstract

Pachytene piRNAs are the most abundant piRNAs in mammalian adult testes. They are generated from long precursor transcripts by the primary piRNA biogenesis pathway but the factors involved in pachytene piRNA precursors processing are poorly understood. Here we show that the Tudor domain-containing 5 (TDRD5) protein is essential for pachytene piRNA biogenesis in mice. Conditional inactivation of TDRD5 in mouse postnatal germ cells reveals that TDRD5 selectively regulates the production of pachytene piRNAs from abundant piRNA-producing precursors, with little effect on low-abundant piRNAs. Unexpectedly, TDRD5 is not required for the 5′ end processing of the precursors, but is crucial for promoting production of piRNAs from the other regions of the transcript. Furthermore, we show that TDRD5 is an RNA-binding protein directly associating with piRNA precursors. These observations establish TDRD5 as a piRNA biogenesis factor and reveal two genetically separable steps at the start of pachytene piRNA processing.

Highlights

Pachytene PIWI-interacting RNAs (piRNAs) are the most abundant piRNAs in mammalian adult testes
We discovered that Tudor domain-containing 5 (TDRD5) deficiency genetically uncouples pachytene piRNA precursor 5′ end processing from the remainder the precursor
Our results reveal a function of TDRD5 downstream of piRNA precursor recruitment to intermitochondrial cement (IMC) and upstream of piRNA loading, trimming and maturation

Summary

Introduction

Pachytene piRNAs are the most abundant piRNAs in mammalian adult testes They are generated from long precursor transcripts by the primary piRNA biogenesis pathway but the factors involved in pachytene piRNA precursors processing are poorly understood. Pachytene piRNAs comprise the largest and most diverse population of small non-coding RNAs in the testis with more than two million distinct piRNA species[19] These piRNAs are primarily generated from hundreds of unique genomic loci (piRNA clusters) through a primary processing pathway[3,19,22], and transcription factor A-MYB plays a critical role in driving the transcription of the bulk of pachytene piRNA precursors[19]. The inventory of piRNA biogenesis factors during this period is still not complete[28,29]

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Conclusion