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Oncogenic Ras blocks transforming growth factor-beta-induced cell-cycle arrest by degradation of p27 through a MEK/Erk/SKP2-dependent pathway.
Exp Hematol. 2005 Jul; 33(7):747-57.EH

Abstract

OBJECTIVE

To examine whether oncogenic Ras affects transforming growth factor (TGF)-beta-mediated cell-cycle arrest in hematopoietic cells and the downstream signal transduction pathway involved in the interference with TGF-beta-induced cell-cycle arrest.

MATERIALS AND METHODS

Two leukemic cell lines bearing N-Ras(L61) mutations; HL-60 and TF-1, and the M1 cell line with wt Ras were investigated for their response to TGF-beta. Signal transduction inhibitors, overexpression and RNA interference studies were performed to investigate the involvement of the various proteins.

RESULTS

Although TGF-beta signal transduction was not affected, G0-G1 arrest was absent in HL-60 and TF-1 cells due to the absence of p27. Overexpression of p27 restored TGF-beta-induced cell-cycle arrest, as well as interfering in Ras-mediated signaling. The farnesyl transferase inhibitor L744832 and the MEK inhibitor U0126 both restored p27 levels and cell-cycle arrest in response to TGF-beta. The absence of p27 protein is due to elevated levels of the ubiquitin ligase SKP2, which complexes with and targets p27 for degradation. RNA interference for SKP2 and treatment of these cells with the proteasome inhibitor MG132 restored p27 levels, corresponding with decreasing SKP2 levels after interfering in N-Ras signal transduction. P27, phosphorylated at threonine 187, is nuclear localized in N-Ras-containing cells. Mutation of this residue to alanine rendered p27 insensitive to degradation.

CONCLUSION

N-Ras(L61) transformed cells lack a G0-G1 arrest upon TGF-beta treatment due to absence of p27. p27 is degraded through a MapK-, and SKP2-dependent pathway. Overexpression of p27 results in restoration of cell-cycle arrest upon TGF-beta treatment.

Authors+Show Affiliations

Division of Hematology, Department of Medicine, University Medical Center Groningen, The Netherlands.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15963850

Citation

Schepers, Hein, et al. "Oncogenic Ras Blocks Transforming Growth Factor-beta-induced Cell-cycle Arrest By Degradation of P27 Through a MEK/Erk/SKP2-dependent Pathway." Experimental Hematology, vol. 33, no. 7, 2005, pp. 747-57.
Schepers H, Wierenga AT, Eggen BJ, et al. Oncogenic Ras blocks transforming growth factor-beta-induced cell-cycle arrest by degradation of p27 through a MEK/Erk/SKP2-dependent pathway. Exp Hematol. 2005;33(7):747-57.
Schepers, H., Wierenga, A. T., Eggen, B. J., & Vellenga, E. (2005). Oncogenic Ras blocks transforming growth factor-beta-induced cell-cycle arrest by degradation of p27 through a MEK/Erk/SKP2-dependent pathway. Experimental Hematology, 33(7), 747-57.
Schepers H, et al. Oncogenic Ras Blocks Transforming Growth Factor-beta-induced Cell-cycle Arrest By Degradation of P27 Through a MEK/Erk/SKP2-dependent Pathway. Exp Hematol. 2005;33(7):747-57. PubMed PMID: 15963850.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Oncogenic Ras blocks transforming growth factor-beta-induced cell-cycle arrest by degradation of p27 through a MEK/Erk/SKP2-dependent pathway. AU - Schepers,Hein, AU - Wierenga,Albertus T J, AU - Eggen,Bart J L, AU - Vellenga,Edo, PY - 2005/01/11/received PY - 2005/04/08/revised PY - 2005/04/14/accepted PY - 2005/6/21/pubmed PY - 2005/9/20/medline PY - 2005/6/21/entrez SP - 747 EP - 57 JF - Experimental hematology JO - Exp Hematol VL - 33 IS - 7 N2 - OBJECTIVE: To examine whether oncogenic Ras affects transforming growth factor (TGF)-beta-mediated cell-cycle arrest in hematopoietic cells and the downstream signal transduction pathway involved in the interference with TGF-beta-induced cell-cycle arrest. MATERIALS AND METHODS: Two leukemic cell lines bearing N-Ras(L61) mutations; HL-60 and TF-1, and the M1 cell line with wt Ras were investigated for their response to TGF-beta. Signal transduction inhibitors, overexpression and RNA interference studies were performed to investigate the involvement of the various proteins. RESULTS: Although TGF-beta signal transduction was not affected, G0-G1 arrest was absent in HL-60 and TF-1 cells due to the absence of p27. Overexpression of p27 restored TGF-beta-induced cell-cycle arrest, as well as interfering in Ras-mediated signaling. The farnesyl transferase inhibitor L744832 and the MEK inhibitor U0126 both restored p27 levels and cell-cycle arrest in response to TGF-beta. The absence of p27 protein is due to elevated levels of the ubiquitin ligase SKP2, which complexes with and targets p27 for degradation. RNA interference for SKP2 and treatment of these cells with the proteasome inhibitor MG132 restored p27 levels, corresponding with decreasing SKP2 levels after interfering in N-Ras signal transduction. P27, phosphorylated at threonine 187, is nuclear localized in N-Ras-containing cells. Mutation of this residue to alanine rendered p27 insensitive to degradation. CONCLUSION: N-Ras(L61) transformed cells lack a G0-G1 arrest upon TGF-beta treatment due to absence of p27. p27 is degraded through a MapK-, and SKP2-dependent pathway. Overexpression of p27 results in restoration of cell-cycle arrest upon TGF-beta treatment. SN - 0301-472X UR - https://www.unboundmedicine.com/medline/citation/15963850/Oncogenic_Ras_blocks_transforming_growth_factor_beta_induced_cell_cycle_arrest_by_degradation_of_p27_through_a_MEK/Erk/SKP2_dependent_pathway_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0301-472X(05)00181-5 DB - PRIME DP - Unbound Medicine ER -