Authors: Chunmei Piao, Cha-Kyung Youn, Min Jin, Sang Pil Yoon, In-Youb Chang, Jung Hee Lee and Ho Jin You

Chunmei Piao

DNA Damage Response Network Center; Chosun University School of Medicine; Gwangju, South Korea; Department of Pharmacology; Chosun University School of Medicine; Gwangju, South Korea

Cha-Kyung Youn

DNA Damage Response Network Center; Chosun University School of Medicine; Gwangju, South Korea; Department of Pharmacology; Chosun University School of Medicine; Gwangju, South Korea

Min Jin

DNA Damage Response Network Center; Chosun University School of Medicine; Gwangju, South Korea; Department of Biochemistry; School of Medicine; Yanbian University; Yanji, Jilin, China

Sang Pil Yoon

Department of Anatomy; College of Medicine; Cheju National University; Jeju, Jeju-do, South Korea

In-Youb Chang

DNA Damage Response Network Center; Chosun University School of Medicine; Gwangju, South Korea; Department of Anatomy; Chosun University School of Medicine; Gwangju, South Korea

Jung Hee Lee

Corresponding author: jhlee75@chosun.ac.kr
DNA Damage Response Network Center; Chosun University School of Medicine; Gwangju, South Korea; Department of Cellular and Molecular Medicine; Chosun University School of Medicine; Gwangju, South Korea

Ho Jin You

Corresponding author: hjyou@chosun.ac.kr
DNA Damage Response Network Center; Chosun University School of Medicine; Gwangju, South Korea; Department of Pharmacology; Chosun University School of Medicine; Gwangju, South Korea

Abstract:
The p53R2 protein, a newly identified member of the ribonucleotide reductase family that provides nucleotides for DNA damage repair, is directly regulated by p53. We show that p53R2 is also regulated by a MEK2 (ERK kinase 2/MAP kinase kinase 2)-dependent pathway. Increased MEK1/2 phosphorylation by serum stimulation coincided with an increase in the RNR activity in U2OS and H1299 cells. The inhibition of MEK2 activity, either by treatment with a MEK inhibitor or by transfection with MEK2 siRNA, dramatically decreased the serum-stimulated RNR activity. Moreover, p53R2 siRNA, but not R2 siRNA, significantly inhibits serum-stimulated RNR activity, indicating that p53R2 is specifically regulated by a MEK2-dependent pathway. Co-immunoprecipitation analyses revealed that the MEK2 segment comprising amino acids 65–171 is critical for p53R2–MEK2 interaction, and the binding domain of MEK2 is required for MEK2-mediated increased RNR activity. Phosphorylation of MEK1/2 was greatly augmented by ionizing radiation, and RNR activity was concurrently increased. Ionizing radiation-induced RNR activity was markedly attenuated by transfection of MEK2 or p53R2 siRNA, but not R2 siRNA. These data show that MEK2 is an endogenous regulator of p53R2 and suggest that MEK2 may associate with p53R2 and upregulate its activity.

Received: April 6, 2012; Accepted: July 23, 2012; Published Online: August 16, 2012

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