title: Ribonucleotide reductase small subunit p53R2 suppresses MEK-ERK activity by binding to ERK kinase 2.
abstract: The p53-dependent RR small subunit (p53R2) protein, a newly identified member of the ribonucleotide reductase family, plays a key role in the p53-dependent cellular response to DNA. Several recent studies have suggested that p53R2 also plays an important role in suppressing the invasive potential of human cancer cells. However, the cellular mechanism that regulates invasiveness remains largely unknown. In this study, we show that p53R2 interacts with MEK2 (extracellular signal-regulated kinase (ERK) kinase 2-mitogen-activated protein kinase (MAPK) kinase 2), the molecule immediately upstream of ERK in the Ras-Raf-MAPK signaling cascade. In co-immunoprecipitation and immunofluorescence analyses, we found that p53R2 and MEK2 interact physically in cultured mammalian cells, and that the p53R2 segment comprising amino acids 161-206 is critical for this interaction. Moreover, serum-induced phosphorylation of MEK1/2 and ERK1/2 was greatly augmented in human cancer cells expressing small-interfering RNA against p53R2. On the other hand, phosphorylation of MEK1/2 and ERK1/2 in human cancer cells was markedly attenuated by overexpression of p53R2. Furthermore, MEK2 was required for p53R2 knockdown-induced enhancement of the invasive ability and anchorage-independent growth of human lung cancer H1299 cells. Taken together, these findings show that p53R2 negatively modulates serum-induced MEK-ERK activity and inhibits the MEK-ERK-mediated malignancy potential of human cancer cells.
authors.affiliation: DNA Repair Research Center, Chosun University, Seosuk-dong, Gwangju, South Korea.
authors.forename: C
authors.initials: C
authors.lastname: Piao
authors.forename: M
authors.initials: M
authors.lastname: Jin
authors.forename: H B
authors.initials: HB
authors.lastname: Kim
authors.forename: S M
authors.initials: SM
authors.lastname: Lee
authors.forename: P N
authors.initials: PN
authors.lastname: Amatya
authors.forename: J-W
authors.initials: JW
authors.lastname: Hyun
authors.forename: I-Y
authors.initials: IY
authors.lastname: Chang
authors.forename: H J
authors.initials: HJ
authors.lastname: You
mesh_terms: D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D017077:Culture Media, Conditioned; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048370:MAP Kinase Kinase 2 / Q000235:genetics / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D034741:RNA, Small Interfering; D012264:Ribonucleotide Reductases / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D017077:Culture Media, Conditioned; D034741:RNA, Small Interfering; C405947:RRM2B protein, human; D012264:Ribonucleotide Reductases; D048049:Extracellular Signal-Regulated MAP Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2