Qian Wenliang, Zhang Xing, Yuan Dongqin, Wu Yuting, Li Hao, Wei Ling, Li Zheng, Dai Zongcai, Song Pei, Sun Qiaoling, Zhou Zizhang, Xia Qingyou, Cheng Daojun
Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Biological Science Research Center, Southwest University, Chongqing 400715, China.
State Key Laboratory of Resource Insects, Southwest University, Chongqing 400715, China.
Sci Adv. 2025 Mar 21;11(12):eadq9111. doi: 10.1126/sciadv.adq9111. Epub 2025 Mar 19.
Endoreplication is characterized by multiple rounds of DNA replication without cell division and determines the growth and final size of endoreplicating cells and tissues in eukaryotes. The cyclic ubiquitination and degradation of several cell cycle regulators are required for endoreplication progression. However, the deubiquitinase that deubiquitinates and stabilizes key factors to modulate endoreplication remains unknown. Here, we found in the endoreplicating salivary gland and silk gland that the depletion of ubiquitin-specific peptidase 8 (USP8) led to endoreplication arrest and a decrease in gland size. Mechanistically, we showed that USP8 interacted with the Fizzy-related (Fzr) protein, a conserved master regulator of endoreplication, thereby deubiquitinating and stabilizing Fzr to modulate endoreplication. Moreover, the molecular chaperone heat shock protein 70 (Hsp70) mediated proper folding of Fzr and increased the interaction between Fzr and USP8, thereby promoting the deubiquitination and stabilization of Fzr. Together, our study demonstrates that USP8 and Hsp70 regulate endoreplication by synergistically maintaining Fzr stability though deubiquitination.
核内复制的特征是在不进行细胞分裂的情况下进行多轮DNA复制，并决定了真核生物中进行核内复制的细胞和组织的生长及最终大小。核内复制的进行需要几种细胞周期调节因子的循环泛素化和降解。然而，去泛素化并稳定关键因子以调节核内复制的去泛素酶仍然未知。在此，我们发现在进行核内复制的唾液腺和丝腺中，泛素特异性肽酶8（USP8）的缺失导致核内复制停滞和腺体大小减小。从机制上来说，我们表明USP8与Fizzy相关（Fzr）蛋白相互作用，Fzr是一种保守的核内复制主要调节因子，从而通过去泛素化和稳定Fzr来调节核内复制。此外，分子伴侣热休克蛋白70（Hsp70）介导Fzr的正确折叠并增强Fzr与USP8之间的相互作用，从而促进Fzr的去泛素化和稳定。总之，我们的研究表明USP8和Hsp70通过去泛素化协同维持Fzr稳定性来调节核内复制。
