Whereas mRNA expression of β1i/LMP2 and β2i/MECL-1 was induced in both hosts (Fig. 1A), immunoblot analysis revealed strongly impaired incorporation of both β1i/LMP2 and β2i/MECL-1 into cardiac 20S proteasomes in acute myocarditis in β5i/LMP7-/- mice (Fig. 1B). Here, PSMB9 is linked to myocarditis.