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This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The ubiquitin proteasome system regulates meiotic recombination in yeast through its association with the synaptonemal complex, a 'zipper'-like structure that holds homologous chromosome pairs in synapsis during meiotic prophase I. In mammals, the proteasome activator subunit PA200 targets acetylated histones for degradation during somatic DNA double strand break repair and during histone replacement during spermiogenesis. We investigated the role of the testis-specific proteasomal subunit a4s (PSMA8) during spermatogenesis, and found that PSMA8 was localized to and dependent on the central region of the synaptonemal complex. Accordingly, synapsis-deficient mice show delocalization of PSMA8. Moreover, though Psma8-deficient mice are proficient in meiotic homologous recombination, there are alterations in the proteostasis of several key meiotic players that, in addition to the known substrate acetylated histones, have been shown by a proteomic approach to interact with PSMA8, such as SYCP3, SYCP1, CDK1 and TRIP13. These alterations lead to an accumulation of spermatocytes in metaphase I and II which either enter massively into apoptosis or give rise to a low number of aberrant round spermatids that apoptose before histone replacement takes place ; This work was supported by MINECO (BFU2017-89408-R) and by Junta de Castilla y Leon (CSI239P18). LGH and NFM are supported by European Social Fund/JCyLe grants (EDU/1083/ 2013 and EDU/310/2015) and YBC by a FPI grant from the MINECO (BS-2015-073993). IR was supported by MINECO (BFU2016-80370-P). JAS was supported by MINECO (BFU2014-53681-P). We appreciate the help of Mª Luz Sánchez García for the FACs analysis. The proteomic analysis was performed in the Proteomics Facility of Centro de Investigación del Cáncer, Salamanca, Grant PRB3 (IPT17/0019 - ISCIII-SGEFI / ERDF). CIC-IBMCC is supported by the Programa de Apoyo a Planes Estratégicos de Investigación de Estructuras de Investigación de Excelencia cofunded by the Castilla–León autonomous government and the European Regional Development Fund (CLC– 2017–01). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript