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Cdk5-mediated phosphorylation of c-Myc on Ser-62 is essential in transcriptional activation of cyclin B1 by cyclin G1.

Seo HR, Kim J, Bae S, Soh JW, Lee YS - J. Biol. Chem. (2008)

Bottom Line: It has been reported previously that cyclin G1 enables cells to overcome radiation-induced G(2) arrest and increased cell death and that these effects are mediated by transcriptional activation of cyclin B1.Furthermore, cyclin G1 mediated increased radiosensitivity, and radiation-induced M phase arrest was attenuated when RNA interference of Cdk5 was treated.Taken together, the results of this study indicate that Cdk5 activation in cells that overexpress cyclin G1 leads to c-Myc phosphorylation on Ser-62, which is responsible for cyclin G1-mediated transcriptional activation of cyclin B1.

View Article: PubMed Central - PubMed

Affiliation: Division of Radiation Effect, Korea Institute of Radiological and Medical Sciences, Seoul 139-706, Korea.

ABSTRACT
It has been reported previously that cyclin G1 enables cells to overcome radiation-induced G(2) arrest and increased cell death and that these effects are mediated by transcriptional activation of cyclin B1. In this study, we further investigated the mechanism by which cyclin G1 transcriptionally activates cyclin B1. Deletion or point mutations within the cyclin B1 promoter region revealed that the c-Myc binding site (E-box) is necessary for cyclin G1-mediated transcriptional activation of cyclin B1 to occur. In addition, the kinase activity of Cdk5 was increased by cyclin G1 overexpression, and Cdk5 directly phosphorylated c-Myc on Ser-62. Furthermore, cyclin G1 mediated increased radiosensitivity, and radiation-induced M phase arrest was attenuated when RNA interference of Cdk5 was treated. Taken together, the results of this study indicate that Cdk5 activation in cells that overexpress cyclin G1 leads to c-Myc phosphorylation on Ser-62, which is responsible for cyclin G1-mediated transcriptional activation of cyclin B1.

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Amino-terminal sequence of c-Myc is the binding site for interaction with Cdk5. A, pcDNA3 and c-Myc were transfected to H460 cells, and Western blot or immunoblotting (IB) was conducted following immunoprecipitation (IP). B, various deletion constructs of hemagglutinin (HA)-tagged c-Myc (left) were transfected to H460 cells. Western blot or immunoblotting was performed following immunoprecipitation (right).
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fig6: Amino-terminal sequence of c-Myc is the binding site for interaction with Cdk5. A, pcDNA3 and c-Myc were transfected to H460 cells, and Western blot or immunoblotting (IB) was conducted following immunoprecipitation (IP). B, various deletion constructs of hemagglutinin (HA)-tagged c-Myc (left) were transfected to H460 cells. Western blot or immunoblotting was performed following immunoprecipitation (right).

Mentions: Binding Site of c-Myc in the Interaction with Cdk5—The binding of c-Myc with Cdk5 was detected in the immunoprecipitates of NCI-H460 cells following transfection with c-Myc (Fig. 6A); therefore, we evaluated the binding activity of several deletion constructs of c-Myc. The F4 fragment was found to bind to Cdk5; however, no interactions were observed between Cdk5 and fragments F1, F2, and F3 (Fig. 6B). These findings indicate that amino acid sequence 1–100 of the amino terminus of c-Myc is the binding site that interacts with Cdk5.


Cdk5-mediated phosphorylation of c-Myc on Ser-62 is essential in transcriptional activation of cyclin B1 by cyclin G1.

Seo HR, Kim J, Bae S, Soh JW, Lee YS - J. Biol. Chem. (2008)

Amino-terminal sequence of c-Myc is the binding site for interaction with Cdk5. A, pcDNA3 and c-Myc were transfected to H460 cells, and Western blot or immunoblotting (IB) was conducted following immunoprecipitation (IP). B, various deletion constructs of hemagglutinin (HA)-tagged c-Myc (left) were transfected to H460 cells. Western blot or immunoblotting was performed following immunoprecipitation (right).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2414302&req=5

fig6: Amino-terminal sequence of c-Myc is the binding site for interaction with Cdk5. A, pcDNA3 and c-Myc were transfected to H460 cells, and Western blot or immunoblotting (IB) was conducted following immunoprecipitation (IP). B, various deletion constructs of hemagglutinin (HA)-tagged c-Myc (left) were transfected to H460 cells. Western blot or immunoblotting was performed following immunoprecipitation (right).
Mentions: Binding Site of c-Myc in the Interaction with Cdk5—The binding of c-Myc with Cdk5 was detected in the immunoprecipitates of NCI-H460 cells following transfection with c-Myc (Fig. 6A); therefore, we evaluated the binding activity of several deletion constructs of c-Myc. The F4 fragment was found to bind to Cdk5; however, no interactions were observed between Cdk5 and fragments F1, F2, and F3 (Fig. 6B). These findings indicate that amino acid sequence 1–100 of the amino terminus of c-Myc is the binding site that interacts with Cdk5.

Bottom Line: It has been reported previously that cyclin G1 enables cells to overcome radiation-induced G(2) arrest and increased cell death and that these effects are mediated by transcriptional activation of cyclin B1.Furthermore, cyclin G1 mediated increased radiosensitivity, and radiation-induced M phase arrest was attenuated when RNA interference of Cdk5 was treated.Taken together, the results of this study indicate that Cdk5 activation in cells that overexpress cyclin G1 leads to c-Myc phosphorylation on Ser-62, which is responsible for cyclin G1-mediated transcriptional activation of cyclin B1.

View Article: PubMed Central - PubMed

Affiliation: Division of Radiation Effect, Korea Institute of Radiological and Medical Sciences, Seoul 139-706, Korea.

ABSTRACT
It has been reported previously that cyclin G1 enables cells to overcome radiation-induced G(2) arrest and increased cell death and that these effects are mediated by transcriptional activation of cyclin B1. In this study, we further investigated the mechanism by which cyclin G1 transcriptionally activates cyclin B1. Deletion or point mutations within the cyclin B1 promoter region revealed that the c-Myc binding site (E-box) is necessary for cyclin G1-mediated transcriptional activation of cyclin B1 to occur. In addition, the kinase activity of Cdk5 was increased by cyclin G1 overexpression, and Cdk5 directly phosphorylated c-Myc on Ser-62. Furthermore, cyclin G1 mediated increased radiosensitivity, and radiation-induced M phase arrest was attenuated when RNA interference of Cdk5 was treated. Taken together, the results of this study indicate that Cdk5 activation in cells that overexpress cyclin G1 leads to c-Myc phosphorylation on Ser-62, which is responsible for cyclin G1-mediated transcriptional activation of cyclin B1.

Show MeSH