HCV core protein stimulates cell growth by downregulating p16 levels via PA28γ-mediated proteasomal degradation. HepG2-vector and HepG2-core protein cells seeded at 2 × 105 cells per well in 6-well plates were transfected with the indicated amount of PA28γ expression plasmid, SC shRNA plasmid, PA28γ shRNA plasmid, and p16 expression plasmid for 48 h. Cells were subjected to BrdU incorporation (A, C) and MTT assays (B, D) (n = 6).