Guo Pengjuan, Song Sha, Niu Yuxiao, Kuang Xiaoyu, Zhou Dafa, Zhou Zizhang, Zhang Yanxiao, Ma Xianjue
Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China.
School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.
Oncogene. 2025 Apr 2. doi: 10.1038/s41388-025-03348-6.
Alternative splicing is a fundamental mechanism that generates functionally distinct proteins from individual genes, contributing to gene regulation and proteomic diversity. In Drosophila, the bunched (bun) gene, a member of the TSC-22 domain gene family, undergoes alternative splicing, yielding diverse protein isoforms involved in crucial biological processes. Nevertheless, the specific roles and regulatory mechanisms of each isoform remain elusive. Here, we employed CRISPR/Cas9 technology to introduce targeted deletions within the endogenous locus of the bun gene, resulting in the removal of either long or short isoforms. We discovered that the short isoforms demonstrated a growth-suppressive role, whereas the long isoforms exhibited a growth-promoting effect. Surprisingly, the long isoforms exhibited a remarkable dual functionality, as both deletion and amplification of long isoform expression impede the excess growth induced by Hippo pathway inactivation. Mechanistically, ectopically expressed Bun long isoforms act as the transcriptional suppressor by competitively binding to targets' promoter regions in conjunction with Yorkie/Scalloped (Yki/Sd), thereby inhibiting its transcriptional outputs and ultimately leading to the growth suppression. These findings unveil the intricate interaction between distinct spliced isoforms of Bun and oncogenic outcomes, highlighting Bun long isoforms as the critical transcription suppressor regulating Hippo pathway inactivation-mediated growth and tumorigenesis in Drosophila.
可变剪接是一种基本机制，可从单个基因产生功能不同的蛋白质，有助于基因调控和蛋白质组多样性。在果蝇中，成束（bun）基因是TSC-22结构域基因家族的成员，会发生可变剪接，产生参与关键生物学过程的多种蛋白质异构体。然而，每种异构体的具体作用和调控机制仍不清楚。在这里，我们利用CRISPR/Cas9技术在bun基因的内源性位点引入靶向缺失，从而去除长或短异构体。我们发现短异构体具有生长抑制作用，而长异构体则表现出促进生长的作用。令人惊讶的是，长异构体表现出显著的双重功能，因为长异构体表达的缺失和扩增都会阻碍由Hippo信号通路失活诱导的过度生长。从机制上讲，异位表达的Bun长异构体通过与Yorkie/Scalloped（Yki/Sd）结合竞争性地结合靶标的启动子区域，从而作为转录抑制因子发挥作用，从而抑制其转录输出并最终导致生长抑制。这些发现揭示了Bun不同剪接异构体与致癌结果之间的复杂相互作用，突出了Bun长异构体作为调节果蝇中Hippo信号通路失活介导的生长和肿瘤发生的关键转录抑制因子。
