ISGylation is a protein post-translational modification (PTM) induced by interferon. ISGylation specifically refers to the covalent association of the ubiquitin-like protein molecule interferon-stimulated gene15 (ISG15) with other molecules. ISGylation has been found to play an important role in viral infections, tumors, neurodegenerative diseases, inflammatory diseases, and other disorders. Creative Biolabs provides ISGylation-specific antibody development services to facilitate the progress of ISGylation research.
ISG15 is a ubiquitin-like protein molecule (UBL) induced by interferon with a molecular weight size of approximately 15 kDa. ISG15 consists of two small ubiquitin-like subunits linked by a short hinge region, and its amino acid sequence shows 50% homology to ubiquitin. ISG15 is the first identified ubiquitin-like protein that functions not only as a free intracellular or extracellular molecule but also as a post-translational modifier during the ISG15 coupling (ISGylation) process and plays a multifaceted role as a post-translational modifier.
The expression of ISG15 and the enzymes involved in ISGylation and deISGylation are affected by IFNs, viral and bacterial infections, and the stress of DNA damage. ISG15 is present in an immature precursor form. It is further processed by proteases into the mature form. Processing by proteases results in exposure to the carboxy-terminal LRLRGG pattern, which is essential for its binding to the target protein. Similar to ubiquitination, ISGylation utilizes a three-step enzymatic reaction. ISG15 is activated by the E1 activating enzyme UBE1L in the presence of ATP and subsequently binds to UBE1L via a thioester bond. After ISG15 is activated, it is transferred to the active site cysteine of the E2 binding enzyme UbcH8 and then to the target protein with the help of E3 ligases, such as HHARI, TRIM25, or HERC5. USP18 reverses ISGylation by cleaving ISG15, which binds to the target protein via an isopeptide bond.
ISGylation is of great importance in disease treatment. IFN-induced ISG15 and its covalent form were found to be central players in the process of viral infection. ISGylation can achieve antiviral effects by modulating IRF3-mediated antiviral responses, inhibiting host protein-viral protein interactions, and regulating immune signaling pathways and other pathways. In cancer, ISGylation is widely involved in human immunity and tumor development. However, according to current findings, ISGylation exhibits both pro-tumor effects and tumor suppressive effects. The exact effect of ISGylation needs to be judged according to different pathological processes.
ISGylation-specific antibodies can be effectively developed using hybridoma technology and phage display technology. However, as with all PTM specific antibodies, the development of ISGylation-specific antibodies has not been an easy task. ISGylation-specific antibodies are primarily directed against the ISG15 protein and can detect endogenous levels of free and coupled ISG15 proteins. A good ISGylation-specific antibody does not cross-react with other ubiquitinated modifications. After obtaining the antibody, it can be detected by mass spectrometry, chromatography, and other techniques. Additionally, the specificity and cross-reactivity of the antibody should be verified by western blotting, immunohistochemistry, and other techniques using the ISG15 protein.
Creative Biolabs has a wealth of knowledge and experience in PTM-specific antibody discovery. We would be happy to discuss our knowledge and experience in ISGylation specific antibody development with you.
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