ISG15 and acute myocarditis: ISG15 is a ubiquitin-like protein upregulated at both the mRNA and protein levels in patients with acute myocarditis and inflammatory cardiomyopathy49, and is conjugated to a variety of proteins (called ISGylation) by specific E1-E2-E3 ubiquitin cascade enzymes when cells are treated with type I IFN50.