Screen for ISG15-crossreactive deubiquitinases.
André Catic1, Edda Fiebiger, Gregory A Korbel
1Program in Immunology, Harvard Medical School, Boston, Massachusetts, United States of America; Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.
Deubiquitinating proteases (DUBs) can process both ubiquitin and ISG15, a ubiquitin-like modifier. This suggests functional overlap in post-translational modification pathways.
Area of Science:
- Biochemistry
- Molecular Biology
- Cellular Biology
Background:
- Ubiquitin-like molecules (UbLs) share similarities with ubiquitin.
- ISG15, a ubiquitin homolog, is upregulated by type I interferon and conjugates to proteins.
- Deubiquitinating proteases (DUBs) reverse ubiquitin and UbL modifications.
Purpose of the Study:
- To investigate if DUBs can process ISG15.
- To identify DUBs that recognize both ubiquitin and ISG15.
Main Methods:
- Cloned and expressed 22 human USP family DUBs.
- Utilized suicide inhibitors specific to ubiquitin and ISG15.
Main Results:
- Identified USP2, USP5, USP13, and USP14 as ISG15-reactive DUBs.
- Confirmed USP18 as an ISG15-specific protease.
- USP14, a proteasome-associated DUB, showed increased ISG15 isopeptidase activity when complexed with the proteasome.
Conclusions:
- ISG15 utilizes the deconjugating machinery of ubiquitin.
- Functional overlap exists between ubiquitin and ISG15 modification pathways.
- This overlap may explain the mild phenotype of ISG15-deficient mice.
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