A Novel Peptide Targeting the USP25 – SIRT1 Interaction Activates SIRT1 to Suppress Cell Senescence

ABSTRACT The deacetylase SIRT1 is a critical regulator of cellular senescence, and the excessive accumulation of senescent cells can further drive the onset of organismal aging. SIRT1 activity is tightly governed by posttranslational modifications, including ubiquitination. While ubiquitination has been well documented to control SIRT1 protein stability, the precise regulatory pathway underlying SIRT1 activity remains poorly understood. Here, we identify the deubiquitinase USP25 as a central regulator of cellular senescence. Specifically, USP25 deficiency in mice mitigates age‐related phenotypes and improves overall physiological function. Mechanistically, USP25 directly interacts with SIRT1 and mediates its deubiquitylation via K63‐linked polyubiquitination, specifically targeting SIRT1 lysine residues K506 and K513, which ultimately suppresses SIRT1 deacetylase activity. Reduced SIRT1 deacetylase activity, in turn, increases P53 or PGC1α acetylation, which further increases the transcriptional activation of downstream target genes and consequently accelerates cellular senescence. Furthermore, we developed a cell‐penetrating peptide, pSirt1‐4, that efficiently disrupts the USP25–SIRT1 interaction, increases SIRT1 deacetylase activity, and attenuates cellular senescence. Collectively, our findings establish USP25 as a critical regulator of aging and highlight the USP25–SIRT1 axis as a promising therapeutic target for treating senescence‐related diseases.