PML and infection: Additionally, we identified two HBV core fractions during infection: the unSUMOylated, soluble HBV core, which is probably involved in pgRNA encapsidation and assembly of progeny virions (48, 52, 53), and the SUMO-conjugated insoluble HBV core fraction, which is associated with the nuclear matrix of the infected cell with specific, but not all, PML-NBs inside the nucleus.