- Deubiquitinating enzymes (DUBs) are specialised proteases that remove ubiquitin molecules from proteins, thereby reversing ubiquitination and regulating protein stability, activity, and localisation. They play a central role in maintaining protein homeostasis by controlling the balance between ubiquitination and deubiquitination. Through this regulatory function, DUBs influence essential cellular processes such as protein degradation, DNA repair, signal transduction, and cell‑cycle progression. Their activity is tightly controlled, as dysregulation can lead to pathological conditions including cancer, neurodegeneration, and immune disorders. DUBs therefore represent a critical component of ubiquitin signalling and cellular regulation.
- DUBs are classified into several families based on their structural domains and catalytic mechanisms. The major families include ubiquitin‑specific proteases (USPs), ubiquitin C‑terminal hydrolases (UCHs), ovarian tumour domain proteases (OTUs), Machado–Joseph disease proteases (MJDs), and JAMM/MPN metalloproteases. Most DUBs are cysteine proteases, while JAMM family members are metalloproteases that require zinc for catalytic activity. Each family exhibits distinct substrate preferences and regulatory functions, allowing precise control over ubiquitin signalling pathways. This diversity ensures that cells can fine‑tune ubiquitin dynamics in response to physiological and environmental cues.
- DUBs regulate protein degradation by modulating the ubiquitin–proteasome system (UPS). Ubiquitination typically marks proteins for destruction by the proteasome, but DUBs can remove these tags, rescuing proteins from degradation. This selective editing of ubiquitin chains allows cells to adjust protein turnover rates and maintain proper levels of regulatory proteins. For example, certain DUBs stabilise cell‑cycle regulators, transcription factors, or signalling proteins by preventing their premature degradation. Through this mechanism, DUBs contribute to dynamic cellular responses and ensure precise control of biological pathways.
- Beyond protein degradation, DUBs play important roles in DNA damage repair. Several DUBs remove ubiquitin from histones and DNA repair factors, thereby regulating chromatin structure and facilitating access to damaged sites. This activity ensures accurate repair of double‑strand breaks and maintains genomic stability. DUBs also participate in immune signalling by modulating ubiquitination of key adaptor proteins involved in inflammatory pathways. Their ability to regulate both activation and termination of immune responses highlights their importance in maintaining immune balance.
- Dysregulation of DUB activity is associated with numerous diseases. Overactive DUBs may stabilise oncogenic proteins, contributing to tumour growth and resistance to therapy. Conversely, loss of DUB function can lead to accumulation of misfolded or toxic proteins, contributing to neurodegenerative disorders such as Parkinson’s and Alzheimer’s disease. Because of their central role in protein homeostasis, DUBs have emerged as promising therapeutic targets. Small‑molecule inhibitors of specific DUBs are currently under investigation for cancer treatment, while other strategies aim to modulate DUB activity to restore cellular balance in degenerative diseases.
- Overall, deubiquitinating enzymes are essential regulators of ubiquitin signalling and protein homeostasis. Their ability to edit ubiquitin chains, rescue proteins from degradation, and modulate key cellular pathways underscores their importance in maintaining cellular health. Understanding DUB biology provides valuable insight into disease mechanisms and offers new opportunities for therapeutic intervention.
