DUB-1, a deubiquitinating enzyme with growth-suppressing activity

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Cytokines are crucial regulators of cell growth, mediating their effects through the induction of specific target genes.
• The identification of novel genes involved in cytokine signaling pathways is essential for understanding cell growth regulation.

Purpose of the Study:

• To clone and characterize a novel cytokine-inducible immediate early gene.
• To investigate the function of the cloned gene, DUB-1, in cell cycle regulation.

Main Methods:

• Differential display method was used to identify cytokine-inducible genes.
• Cloning and expression of the DUB-1 gene.
• Biochemical assays using glutathione S-transferase-DUB-1 fusion protein to assess deubiquitinating activity.
• Site-directed mutagenesis (C60S) to abolish enzymatic activity.
• Induction of DUB-1 expression using a steroid-inducible promoter to study cell cycle effects.

Main Results:

• A novel cytokine-inducible immediate early gene, DUB-1 (deubiquitinating enzyme-1), was cloned.
• DUB-1 demonstrated deubiquitinating activity, cleaving ubiquitin from a model substrate.
• Mutation of a conserved cysteine residue (C60S) abolished DUB-1's enzymatic activity.
• Continuous DUB-1 expression induced G1 phase cell cycle arrest, with cells remaining viable.
• Cessation of DUB-1 expression allowed cells to resume proliferation.

Conclusions:

• DUB-1 is a functional deubiquitinating enzyme involved in cell cycle regulation.
• DUB-1 plays a role in controlling cellular growth, likely by modulating ubiquitin-dependent proteolysis or the ubiquitination status of growth regulatory factors.
• DUB-1 represents a potential target for understanding and manipulating cell proliferation.