# The dual role of Spn-E in supporting heterotypic ping-pong piRNA amplification in silkworms

## TL;DR

This study reveals that Spn-E has two roles in the piRNA pathway of silkworms, helping to regulate gene silencing in the germline.

## Contribution

The study identifies Spn-E's dual role in supporting and regulating the ping-pong piRNA cycle in silkworms.

## Key findings

- Spn-E uses its ATPase activity to support BmAgo3-dependent production of Siwi-bound piRNAs.
- Spn-E suppresses homotypic Siwi–Siwi ping-pong independently of its ATPase activity.
- Spn-E facilitates proper heterotypic ping-pong between Siwi and BmAgo3 in silkworms.

## Abstract

The PIWI-interacting RNA (piRNA) pathway plays a crucial role in silencing transposons in the germline. piRNA-guided target cleavage by PIWI proteins triggers the biogenesis of new piRNAs from the cleaved RNA fragments. This process, known as the ping-pong cycle, is mediated by the two PIWI proteins, Siwi and BmAgo3, in silkworms. However, the detailed molecular mechanism of the ping-pong cycle remains largely unclear. Here, we show that Spindle-E (Spn-E), a putative ATP-dependent RNA helicase, is essential for BmAgo3-dependent production of Siwi-bound piRNAs in the ping-pong cycle and that this function of Spn-E requires its ATPase activity. Moreover, Spn-E acts to suppress homotypic Siwi–Siwi ping-pong, but this function of Spn-E is independent of its ATPase activity. These results highlight the dual role of Spn-E in facilitating proper heterotypic ping-pong in silkworms.

Spn-E promotes BmAgo3-dependent production of Siwi-bound piRNAs using its ATPase activity while suppressing Siwi-Siwi homotypic ping-pong, thereby facilitating proper heterotypic ping-pong in silkworms.

Spn-E promotes proper heterotypic ping-pong between Siwi and BmAgo3 in silkworms.Spn-E’s ATPase activity is required for BmAgo3-dependent production of Siwi-bound piRNAs.Spn-E suppresses Siwi-Siwi homotypic ping-pong independently of its ATPase activity.

Spn-E promotes proper heterotypic ping-pong between Siwi and BmAgo3 in silkworms.

Spn-E’s ATPase activity is required for BmAgo3-dependent production of Siwi-bound piRNAs.

Spn-E suppresses Siwi-Siwi homotypic ping-pong independently of its ATPase activity.

Spn-E promotes BmAgo3-dependent production of Siwi-bound piRNAs using its ATPase activity while suppressing Siwi-Siwi homotypic ping-pong, thereby facilitating proper heterotypic ping-pong in silkworms.