Fig. 3

p16 enhanced ubiquitin-dependent degradation of AE2 protein. a AE2 expression in two GC cell lines treated with CHX (25 μg/ml for SGC7901 cells and 50 μg/ml for MKN28 cells) for the indicated times (left). The ratio of AE2 protein abundance to that of β-actin was normalized to a value of 1.0 for 0 h (right). Data are representative of experiments performed three times in triplicate. AE2 was more stable in MKN28 cells than in SGC7901 cells. b AE2 expression in two GC cell lines treated with 10 μM MG132 for the indicated times (left). Data are representative of experiments performed three times in triplicate. The ratio of AE2 protein abundance to that of β-actin was normalized to a value of 1.0 for 0 h (right). AE2 protein was more susceptible to degradation in SGC7901 cells than in MKN28 cells. c p16 enhanced ubiquitin-dependent degradation of the AE2 protein. HEK293T cells were co-transfected with vectors expressing pEGFP-AE2a, HA-Ub and p16, singly or in combination, as indicated. At 42 h after transfection, cells were treated with 10 μM MG132 for 6 h. Cell extracts were immunoprecipitated with anti-GFP antibodies to reveal polyubiquitination