CircuLex Human ISG15 ELISA Kit

ISG15 (Interferon (IFN)-Stimulated Gene 15) is a ubiquitin-like protein containing two ubiquitin homology domains and becomes conjugated to a variety of proteins when cells are treated with type I interferon or lipopolysaccharide. Therefore this modification (so called, ISGylation) appear to be involved in type I interferon signal transduction. Unlike ubiquitylation, ISGylation does not drive protein degradation (regulated by K48-linked ubiquitin). ISG15 is expressed as a 165 amino acid precursor that is subsequently processed to expose the C-terminal sequence LRLRGG. Like ubiquitin, this C-terminal diglycine residue is adenlylated and conjugated by a thiolester bond to sequential cystine residues on the E1-activating, E2-carrier and E3-ligase enzymes, before being transferred to lysine residues on target protein substrates. ISG15 can also be found extracellularly in an unconjugated form (free form). Human lymphocytes and monocytes were reported to release free ISG15 following treatment with IFN-β. More than 50 % of the total ISG15 could be detected in the culture medium after 24 hours following IFN stimulation. In addition, ISG15 is highly elevated and extensively conjugated to cellular proteins in many tumors and tumor cell lines. The increased levels of ISG15 in tumor cells were found to be associated with decreased levels of polyubiquitinated proteins.

The CycLex Research Product CircuLex Human ISG15 ELISA kit is used for the quantitative measurement of human ISG15 in cell lysate, culture medium and human serum.

Microplate, 10X Wash Buffer, Dilution Buffer, Human ISG15 Standard, HRP conjugated Detection Antibody, Substrate Reagent, Stop Solution

0.188 ng/mL to 12 ng/ml

better than 0.85 ng/ml of sample.

ISG15