Figure 9 | Oncogene

Figure 9

From: ΔMEKK3:ER* activation induces a p38α/β2-dependent cell cycle arrest at the G2 checkpoint

Figure 9

ΔMEKK3:ER* induced G2 block is reversed by SB203580 irrespective of p21CIP1 status. (a) CM3.3 cells released from S phase were immediately treated with either 5 μM SB203580 (SB) or 10 μM U0126 (UO). Thirty min later 100 nM 4-HT was administered to these cells for the designated times and the cell cycle profiles were compared using PI staining and flow cytometry. (b) The number of cells in G2/M or G1 from (a) is quantified and shown graphically. (c) CM3.3 cells were left cycling (Cyc), blocked with aphidicolin (Aph) or released from aphidicolin for 20 h in the presence or absence of 4-HT, U0126 or SB203580 as indicated. Whole cell lysates were immunoblotted with antibodies specific for p21CIP1 or phospho-ERK1/2, ERK1/2, phospho-Ser63-cJun and phospho-p38. (d) CM3.3 cells were released from an aphidicolin block and left untreated (Con), or treated with 4-HT with or without SB203580. After 15 h cells were lysed and assayed for cyclin B-associated histone kinase activity. The data are the mean±s.d. of three independent determinations and the asterisk * indicates a significant difference by t-test (P=0.002). In addition, whole cell lysates were also immunoblotted for the presence cyclin B. (e) The effect of 5 μM SB203580 pre-treatment on the ΔMEKK3:ER* derived G2 arrest observed in RM3.21 cells was determined by quantifying the mitotic index

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