FIG 9.

p62 contributes to LCL outgrowth and proliferation. (A and B) shRNA-mediated p62 deficiency promotes etoposide-induced cell death. IB4 cell lines stably expressing p62 shRNA#1 and shRNA#2 (or control shRNA) were induced by 1 μg/ml doxycycline for 4 days, followed by treatment with etoposide at different concentrations and for different times (A) and with 5 μM etoposide (B). Doxycycline was replaced every 4 days to maintain shRNA expression. Early and late apoptosis was evaluated, and representative results are shown. (C and D) p62 deficiency reduces cell proliferation, which can be rescued in part by wild-type p62 or the phosphorylation-deficient mutant p62(S349/403A). IB4 cell lines stably expressing p62 shRNA#2 targeting the 3′ UTR (or control shRNA) were transfected with Flag-p62 or Flag-p62(S349/403A) using a Nucleofector B cell kit (Lonza); 1 μg/ml doxycycline was added to induce shRNA expression at the time of transfection. Cell proliferation was measured for up to 8 days with doxycycline.