Figure 5.

Fractionation of mitotic ER and Golgi after treatment with brefeldin A during progression to M-phase. Subconfluent cultures of HeLa cells were treated with 0.5 μg/ml nocodazole in the absence (A) or presence (B) of 10 μg/ml brefeldin A for 24 h. Mitotic cells were obtained by shake-off, and the postnuclear supernatants were fractionated on glycerol velocity gradients as indicated above. The recovery, in each fraction, of the Golgi marker GPP130 and the ER marker p63 was determined by densitometry of immunoblots. Unlike nontreated mitotic cells, cells that progressed to M-phase during brefeldin A treatment lacked the 115 S major mitotic Golgi breakdown product. Instead, the mitotic Golgi was completely recovered at the bottom of the gradient together with the ER.