The enzyme exists as a large, 700-kD multi-subunit complex (Lees et al., 2017b; Dornan et al., 2018); however, the isolated carboxy-terminal fragment containing the helical and catalytic domain (PI4KAC1001) retains activity and can complement hepatitis C proliferation in PI4KA knockdown cells (Harak et al., 2014). The gene discussed is PI4KA; the disease is hepatitis C virus infection.