ERK1/2 and p38 cooperate to induce a p21CIP1-dependent G1 cell cycle arrest.
To study the mechanisms by which mitogen- and stress-activated protein kinases regulate cell cycle re-entry, we have used a panel of conditional kinases that stimulate defined MAPK or SAPK cascades. Activation of DeltaMEKK3:ER* during serum restimulation of quiescent cells causes a strong activation of JNK1 and p38alpha but only a modest potentiation of serum-stimulated ERK1/2 activity. In CCl39 cells this promoted a sustained G1 arrest that correlated with decreased expression of cyclin D1 and Cdc25A, increased expression of p21CIP1 and inhibition of CDK2 activity. In Rat-1 cells, in which p21(CIP1) expression is silenced by methylation, DeltaMEKK3:ER* activation caused only a transient delay in the S phase entry rather than a sustained G1 arrest. Furthermore, p21CIP1-/- 3T3 cells were defective for the DeltaMEKK3:ER*-induced G1 cell cycle arrest compared to their wild-type counterparts. These results suggest that activated DeltaMEKK3:ER* inhibits the G1 --> S progression by two kinetically distinct mechanisms, with expression of p21CIP1 being required to ensure a sustained G1 cell cycle arrest. The ERK1/2 and p38alphabeta pathways cooperated to induce p21CIP1 expression and inhibition of p38alphabeta caused a partial reversal of the cell cycle arrest. In contrast, selective activation of ERK1/2 by DeltaRaf-1:ER* did not inhibit serum stimulated cell cycle re-entry. Finally, selective activation of JNK by DeltaMEKK1:ER* failed to inhibit cell cycle re-entry, even in cells that retained wild-type p53, arguing against a major role for JNK alone in antagonizing the G1 --> S transition.
Signalling Programme, The Babraham Institute, Babraham Hall, Cambridge CB2 4AT, UK.
Daniel E
DE
Todd
Ruth M
RM
Densham
Sarah A
SA
Molton
Kathryn
K
Balmanno
Catherine
C
Newson
Claire R
CR
Weston
Andrew P
AP
Garner
Linda
L
Scott
Simon J
SJ
Cook
D016475:3T3 Cells; D000818:Animals; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000494:pharmacology / Q000502:physiology*; D016193:G1 Phase; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D016160:Retinoblastoma Protein / Q000378:metabolism; D016196:S Phase; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases
C493957:Cdkn1a protein, mouse; C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D013629:Tamoxifen; C016601:afimoxifene; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases