Figure 2. α3 regulates α4-α4 proteasome assembly in human cells.
(A) Cartoon illustrating regions of the α3 gene targeted by different shRNAs.
(B) shRNA-mediated knockdown of α3 in stable α4-CC-Flag (HeLa) cells. The α3-1 shRNA cause a ∼50% decrease in α3 levels. α4-CC-Flag expression was induced by the addition of doxycycline (Dox).
(C) α3 knockdown in α4-CC-Flag stable HeLa cells results in increased assembly of α4-α4 proteasomes. Also see Fig. S2.
(D) Confirmation of the increase in α4-α4 proteasomes upon α3 knockdown using gel-isolated HeLa cell 26S proteasomes.
(E) Ectopic overexpression of α3 in α4-overexpressing HeLa cells causes a decrease in α4-α4 proteasome formation based on α4- α4 crosslinking.
(F) α6-Flag expression was induced in stable α6-Flag HeLa cells by addition of Dox; α4-WT or α4-CC was transiently expressed in these cells.
(G) α6 expression level does not affect α4-α4 proteasome assembly. α6-Flag expression was induced in α6-Flag stable HeLa cells by addition of Dox (see Fig. 2F).