A joint team led by Prof. Wei Xie from the School of Life Sciences at Tsinghua University and Prof. Lin Liu from the School of Life Sciences at Nankai University uncovered a novel mechanism by which Usp17l, a gene family activated during minor zygotic genome activation (ZGA), regulates the 2-cell-like program at both the transcriptional and post-translational levels. Their study, titled "USP17L promotes the 2-cell-like program through deubiquitination of H2AK119ub1 and ZSCAN4", was published in Nature Communications on August 1, 2025. This work provides new insights into ZGA, the 2-cell program, and totipotency.
ZGA is the first transcriptional event after fertilization, marking the transition from maternal to zygotic control of development. In mice, this process occurs in two phases: a minor ZGA at the late 1-cell to early 2-cell stage, and a major ZGA in the late 2-cell stage. Dozens of genes are activated during minor ZGA ("2C genes"), which are essential for initiating the major ZGA and for early development. A rare subpopulation (1-5%) of mouse embryonic stem cells (mESCs), known as 2-cell-like cells (2CLCs), shares some features with 2-cell embryos, including 2C gene activation and chromatin accessibility. However, the functions and the underlying mechanisms of minor ZGA genes in embryos and 2CLCs remain poorly understood.
In this study, the authors identified USP17L as a key regulator of the 2C program. Overexpression of Usp17l promoted, while knockdown suppressed, the 2C-like states. Of note, the induction of 2C genes by USP17L was partially dependent on DUX, a known transcription factor for the 2-cell program. ChIP-seq revealed that the Dux locus was enriched for the repressive histone mark H2AK119ub1, which can be removed by USP17L acting as a deubiquitinase. Such deubiquitination activates Dux, the downstream 2C genes, and the retrotransposon MERVL. Intriguingly, previous studies have shown that Usp17l is also a target of DUX, suggesting a potential positive feedback loop between USP17L and DUX that could rapidly amplify the 2C transcriptional program. Besides transcriptional regulation, USP17L also stabilizes the 2C-specific protein ZSCAN4 by removing its ubiquitination and preventing proteasomal degradation. Overexpression of USP17L increased ZSCAN4 protein levels and the proportion of Zscan4⁺ 2CLCs in mESCs, confirming its role in post-translational control of the 2-cell program.
In embryos, the authors found that H2AK119ub1 levels at the Dux locus were high in oocytes, decreased in zygotes and early 2-cell embryos (when Dux is active), and increased again and remained high at later stages. Overexpression of USP17LE in zygotes led to the removal of H2AK119ub1 globally and at the Dux locus, activation of Dux and 2C genes, and ultimately preimplantation developmental arrest.
USP17L regulates the 2-cell like program by deubiquitinating H2AK119ub1 and ZSCAN4
Together, this study reveals that USP17L facilitates the activation and maintenance of the 2-cell program through dual deubiquitination targets-H2AK119ub1 at the Dux locus and ZSCAN4 protein, regulating ZGA and totipotency-like states in mESCs and embryos.
Prof. Lin Liu from Nankai University and Prof. Wei Xie from Tsinghua University are the co-corresponding authors of the study. Dr. Panpan Shi from Nankai University and Dr. Xukun Lu from the Institute of Women, Children and Reproductive Health, Shandong University (a former postdoc in Prof. Xie’s lab), are co-first authors. Kaijiang Jin, Linlin Liu, Guoxing Yin, and Dr. Jiao Yang from Nankai University, Wenying Wang, Lijuan Wang, and Lijun Dong from Tsinghua University made significant contributions. Additional support was provided by the Animal Center and the Bioinformatics Core Facility at Tsinghua University.
This work was supported by the National Key R&D Program of China, the National Natural Science Foundation of China, Haihe Laboratory of Cell Ecosystem Innovation Fund, and the THU-PKU Center for Life Sciences. Prof. Wei Xie is a New Cornerstone Investigator.
Paper link: https://www.nature.com/articles/s41467-025-62303-x
