Abstract
The ubiquitin-proteasome system (UPS) represents an evolutionarily conserved machinery governing proteostasis through spatiotemporal regulation of protein degradation. While spermatogenesis involves multilayered regulatory mechanisms spanning translation to dynamic post-translational modifications (PTMs), the identity of UPS-associated E3 ligases orchestrating germ cell-specific protein turnover remains elusive. Here, we identify a testis-specific E3 ubiquitin ligase complex comprising elongin B/C, Cullin-2 (CUL2), RING-box protein-1 (RBX1), and SOCS box protein ASB9, designated ECSASB9. Genetic ablation of ECSASB9 in mice via ubiquitous Asb9 knockout (KO) or spermatid-specific elongin B/C conditional KO disrupts spermiogenesis and compromises fertility. Mechanistic studies reveal that ECSASB9 engages tubulin beta 4 A (TUBB4A) through substrate recognition, catalyzing K48-linked polyubiquitination at lysine 379 (K379) to promote proteasomal degradation. Notably, Tubb4aK379R knock-in (KI) mice phenocopy the spermiogenesis defects observed upon ECSASB9 deficiency. Clinically, we identify three hemizygous missense variants in X-linked ASB9 among Chinese males with idiopathic infertility. Male mice bearing orthologous ASB9 variant exhibit oligoasthenoteratozoospermia (OAT) and subfertility, mirroring human phenotypes. Taken together, our findings establish ECSASB9 as an important regulator of spermatogenic proteostasis and provide mechanistic insights into UPS-mediated tissue-specific degradation, while implicating ASB9 variants in male infertility pathogenesis.
Data availability
The murine multi-tissue transcriptomic datasets are obtained from the NCBI SRA database repository (https://www.ncbi.nlm.nih.gov/bioproject/?term=PRJNA375882). The mass spectrometry-based proteomics data have been deposited in the ProteomeXchange Consortium via the PRIDE repository (http://www.ebi.ac.uk/pride) under accession codes PXD064742 and PXD064743. Source data are provided with this paper.
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Acknowledgements
We thank Jiahao Sha from Nanjing Medical University for helpful comments. This work was supported by the National Natural Science Foundation of China (82271633 and 82471641 to B.Z., 32370903 to X.H., and 32470899 to J.Y.), the Natural Science Foundation of Jiangsu Province (BK20221376 to J.Y. and BK20230004 to M.L.), and the Natural Science Foundation of Gusu School of Nanjing Medical University (GSKY202510201 to B.Z.).
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T.W.: Data curation, Investigation, Methodology, Validation. C.T.: Data curation, Investigation, Methodology. Y.F.: Investigation, Visualization. W.Q.: Investigation. J.C.: Investigation, Methodology. H.W.: Data curation, Investigation. W.G.: Investigation. B.X.: Investigation. X.Y.: Investigation. M.B.: Investigation. J.X.: Investigation. N.Z.: Investigation. H.H.: Investigation. B.J.: Investigation. Q.X.: Investigation. L.M.: Investigation. C.T.: Investigation. G.L.: Supervision. C.S.: Data curation. X.C.: Data curation. Y.G.: Methodology, Software. T.Z.: Methodology, Software. Y.L.: Supervision. R.H.: Data curation, Investigation. Y.C.: Conceptualization, Supervision. M.L.: Conceptualization, Supervision. J.Y.: Data curation, Funding acquisition, Investigation. X.H.: Conceptualization, Funding acquisition, Supervision. Y.-Q.T.: Conceptualization, Supervision. B.Z.: Conceptualization, Funding acquisition, Project administration, Supervision, Writing – review & editing.
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Wu, T., Tu, C., Feng, Y. et al. A testis-specific E3 ubiquitin ligase complex governs spermiogenesis and male fertility. Nat Commun (2026). https://doi.org/10.1038/s41467-026-70025-x
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DOI: https://doi.org/10.1038/s41467-026-70025-x
