Mouse anti-ISG15 (Sku# 433180) detects human ISG15, and is validated in western blot application, with confirmed reactivity in human and Rat tissues. Reactivity against rhesus monkey and chimpanzee is also expected based on sequence homology.
ISG15 (interferon-induced 17 kDa protein) is a ubiquitin-like protein that is conjugated to intracellular target proteins after IFN-alpha or IFN-beta stimulation. Substrate specificity and interaction with ligating enzymes differs from that of ubiquitin. Conjugation of ISG15 uses E1 enzyme Ube1L, and the difference to ubiquitin pathway happens at the level of E2 enzyme. ISG15 conjugation system favors UbcH8 as its E2 enzyme. ISG15 has a large number of both IFN-induced and constitutively expressed proteins, such as STAT1, SERPINA3G, JAK1, MAPK3⁄ERK1, PLCG1, EIF2AK2⁄PKR, MX1⁄MxA, and RIG-1. ISG15 is deconjugated by USP18⁄UBP43. Recent studies suggest that in addition to being upregulated as a primary response to diverse microbial and cellular stress stimuli, ISG15 is overexpressed in breast carcinoma compared to normal breast tissue. This results in unfavourable prognosis for the patients. ISG15 may thus represent a novel breast tumour marker. ISG15 plays also a role by inhibiting the release of HIV-1 virions upon IFN induction.