Stabilization of 4E-BP1 by PI3K kinase and its involvement in CHK2 phosphorylation in the cellular response to radiation.
Int J Med Sci
; 14(5): 452-461, 2017.
Article
en En
| MEDLINE
| ID: mdl-28539821
ABSTRACT
Objectives:
4E-BP1 is a family member of eIF4E binding proteins (4E-BPs) which act as the suppressors of cap-dependent translation of RNA via competitively associating with cap-bound eIF4E. RNA translation regulation is an important manner to control the cellular responses to a series of stress conditions such as ionizing radiation (IR)-induced DNA damage response and cell cycle controlling. This study aimed to determine the mechanism of 4E-BP1 stabilization and its potential downstream target(s) in the response to IR.Methods:
PI3Ks kinase inhibitors were used to determine the signaling control of 4E-BP1 phosphorylation and protein stability. shRNA strategy was employed to silence the expression of 4E-BP1 in HeLa and HepG2 cells, and determine its effect on the irradiation-induced CHK2 phosphorylation. The protein degradation/stability was investigated by western blotting on the condition of blocking novel protein synthesis by cycloheximide (CHX).Results:
The phosphorylation of 4E-BP1 at Thr37/46 was significantly increased in both HepG2 and HeLa cells by ionizing radiation. Depression of 4E-BP1 by shRNA strategy resulted in an incomplete G2 arrest at the early stage of 2 hours post-irradiation, as well as a higher accumulation of mitotic cells at 10 and 12 hours post-irradiation as compared to the control cells. Consistently, the CHK2 phosphorylation at Thr68 induced by IR was also attenuated by silencing 4E-BP1 expression. Both PI3K and DNA-PKcs kinase inhibitors significantly decreased the protein level of 4E-BP1, which was associated with the accelerated degradation mediated by ubiquitination-proteasome pathway.Conclusion:
PI3K kinase activity is necessary for maintaining 4E-BP1 stability. Our results also suggest 4E-BP1 a novel biological role of regulating cell cycle G2 checkpoint in responding to IR stress in association with controlling CHK2 phosphorylation.Palabras clave
Texto completo:
1
Bases de datos:
MEDLINE
Asunto principal:
Fosfoproteínas
/
Biosíntesis de Proteínas
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Fosfatidilinositol 3-Quinasas
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Proteínas Adaptadoras Transductoras de Señales
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Quinasa de Punto de Control 2
Límite:
Humans
Idioma:
En
Revista:
Int J Med Sci
Asunto de la revista:
MEDICINA
Año:
2017
Tipo del documento:
Article