Ubiquitination and deubiquitination play a critical role in all aspects of cellular processes, and the enzymes involved are tightly regulated by multiple factors including posttranslational modifications like most other proteins. Dysfunction or misregulation of these enzymes could have dramatic physiological consequences, sometimes leading to diseases. Therefore, it is important to have a clear understanding of these regulatory processes. Here, we have reviewed the posttranslational modifications of deubiquitinating enzymes and their consequences on the catalytic activity, stability, abundance, localization, and interaction with the partner proteins.

Cascade enzymatic reactions in living organisms are fundamental reaction mechanisms in coordinating various complex biochemical processes such as metabolism, signal transduction, and gene regulation. Many studies have attempted to mimic cascade reactions using nanoparticles with enzyme-like activity; however, precisely tuning each reaction within complex networks to enhance the catalytic activity remains challenging. Here, we present enzyme-like chiral plasmonic nanoparticles for optically tunable catalytic cancer therapy. We create chiral plasmonic nanoparticles with glucose oxidase (GOD) and peroxidase (POD) activities, followed by introducing circularly polarized light (CPL). By sequentially activating GOD and POD reactions with right-handed CPL (RC) followed by left-handed CPL (LC), we achieve 1.25- and 1.9-fold enhanced catalytic performance (overall 1.3 times enhancement) compared to non-controlled cascade reactions by creating an optimal acidic environment for the subsequent reaction. Moreover, the D-Au nanoparticle shows a 2-fold higher binding selectivity to D-glucose substrates, attributed to chirality matching. In both cell studies and male mouse models, sequentially irradiated groups (RC followed by LC) exhibit the highest radical generation and the most efficient treatment outcomes compared to the other systems under different irradiation conditions. We believe that our system holds strong potential for medical applications, suggesting a promising platform for catalytic therapy.

P53 is activated in response to cellular stresses such as DNA damage, oxidative stress, and especially ribosomal stress. Although the regulations of p53 by E3 ligase and deubiquitinating enzymes (DUBs) have been described, the cellular roles of DUB associated with ribosomal stress have not been well studied. In this study, we report that Ubiquitin Specific Protease 47 (USP47) functions as an important regulator of p53. We show that ubiquitinated ribosomal protein S2 (RPS2) by Mouse double minute 2 homolog (MDM2) is deubiquitinated by USP47. USP47 inhibits the interaction between RPS2 and MDM2 thereby alleviating RPS2-mediated suppression of MDM2 under normal conditions. However, dissociation of USP47 leads to RPS2 binding to MDM2, which is required for the suppression of MDM2, consequently inducing up-regulation of the p53 level under ribosomal stress. Finally, we show that depletion of USP47 induces p53 and therefore inhibits cell proliferation, colony formation, and tumor progression in cancer cell lines and a mouse xenograft model. These findings suggest that USP47 could be a potential therapeutic target for cancer.

Aurora kinase A (AURKA) performs critical functions in mitosis. Thus, the activity and subcellular localization of AURKA are tightly regulated and depend on diverse factors including interactions with the multiple binding cofactors. How these different cofactors regulate AURKA to elicit different levels of activity at distinct subcellular locations and times is poorly understood. Here, we identified a conserved region of CEP192, the major cofactor of AURKA, that mediates the interaction with AURKA. Quantitative binding studies were performed to map the interactions of a conserved helix (Helix-1) within CEP192. The crystal structure of Helix-1 bound to AURKA revealed a distinct binding site that is different from other cofactor proteins such as TPX2. Inhibiting the interaction between Helix-1 and AURKA in cells led to the mitotic defects, demonstrating the importance of the interaction. Collectively, we revealed a structural basis for the CEP192-mediated AURKA regulation at the centrosome, which is distinct from TPX2-mediated regulation on the spindle microtubule.

Inhibition of the molecular chaperone heat shock protein 90 (Hsp90) represents a promising approach for cancer treatment. BIIB021 is a highly potent Hsp90 inhibitor with remarkable anticancer activity; however, its clinical application is limited by lack of potency and response. In this study, we aimed to investigate the impact of replacing the hydrophobic moiety of BIIB021, 4-methoxy-3,5-dimethylpyridine, with various five-membered ring structures on the binding to Hsp90. A focused array of N⁷/N⁹-substituted purines, featuring aromatic and non-aromatic rings, was designed, considering the size of hydrophobic pocket B in Hsp90 to obtain insights into their binding modes within the ATP binding site of Hsp90 in terms of π–π stacking interactions in pocket B as well as outer α-helix 4 configurations. The target molecules were synthesized and evaluated for their Hsp90α inhibitory activity in cell-free assays. Among the tested compounds, the isoxazole derivatives 6b and 6c, and the sole six-membered derivative 14 showed favorable Hsp90α inhibitory activity, with IC₅₀ values of 1.76 µM, 0.203 µM, and 1.00 µM, respectively. Furthermore, compound 14 elicited promising anticancer activity against MCF-7, SK-BR-3, and HCT116 cell lines. The X-ray structures of compounds 4b, 6b, 6c, 8, and 14 bound to the N-terminal domain of Hsp90 were determined in order to understand the obtained results and to acquire additional structural insights, which might enable further optimization of BIIB021.

Background: Cervical cancer remains a major global health concern, with existing chemotherapy facing limited effectiveness owing to resistance. Polo-like kinase 1 (PLK1) overexpression in cervical cancer cells is a promising target for developing novel therapies to overcome chemoresistance and improve treatment efficacy. Methods: In this study, we developed a novel PROTAC, NC1, targeting PLK1 PBD via the N-end rule pathway. Results: This PROTAC effectively depleted the PLK1 protein in HeLa cells by inducing protein degradation. The crystal structure of the PBD-NC1 complex identified key PLK1 PBD binding interactions and isothermal titration calorimetry (ITC) confirmed a binding affinity of 6.06 µM between NC1 and PLK1 PBD. NC1 significantly decreased cell viability with an IC₅₀ of 5.23 µM, induced G2/M phase arrest, and triggered apoptosis in HeLa cells. In vivo, NC1 suppressed tumor growth in a HeLa xenograft mouse model. Conclusions: This research highlights the potential of N-degron-based PROTACs targeting the PLK1 protein in cancer therapies, highlighting their potential in future cervical anticancer treatment strategies.