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. Author manuscript; available in PMC: 2017 Nov 2.
Published in final edited form as: Cell Rep. 2017 Oct 10;21(2):442–454. doi: 10.1016/j.celrep.2017.09.052

Figure 1. Bcl-2 protein levels are down-regulated by the ubiquitin-proteasome system during apoptosis.

Figure 1

A. Apoptosis was induced in HeLa and immortalized MEFs using STS for the indicated times, and endogenous Bcl-2 was detected by Western blot analysis. B. Apoptosis was induced in HeLa, BT-549 and COS-7 cells with etoposide. NT (No Treatment). In primary MEFs apoptosis was induced with 100 µM etoposide for 5 h. A decrease in endogenous Bcl-2 levels was seen upon treatment with both STS and etoposide. C. Apoptosis was induced in HeLa cells using STS in the presence or absence of 20 µM of MG132. Western and densitometry analyses revealed decreased levels of Bcl-2 with STS treatment, and stabilization of Bcl-2 upon MG132 treatment. This suggests that Bcl-2 levels are down-regulated via the UPS. D. WT MEFs and HeLa cells were transiently transfected with Bcl-2, XIAP and ubiquitin and treated with 20 µM MG132 for 6 h and with 1.75 µM STS. IP with anti-Bcl-2 was followed by Western Blotting with anti-ubiquitin antibodies. *Represents the IG heavy chain. Poly-ubiquitylated forms of Bcl-2 appeared in apoptotic cells and correlated with decreased Bcl-2 levels.