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RSK promotes G2/M transition through activating phosphorylation of Cdc25A and Cdc25B.

ABSTRACT: Activation of the mitogen-activated protein kinase (MAPK) cascade in mammalian cell lines positively regulates the G2/M transition. The molecular mechanism underlying this biological phenomenon remains poorly understood. Ribosomal S6 kinase (RSK) is a key downstream element of the MAPK cascade. Our previous studies established roles of RSK2 in Cdc25C activation during progesterone-induced meiotic maturation of Xenopus oocytes. In this study we demonstrate that both recombinant RSK and endogenous RSK in Xenopus egg extracts phosphorylate all three isoforms of human Cdc25 at a conserved motif near the catalytic domain. In human HEK293 and PC-3mm2 cell lines, RSK preferentially phosphorylates Cdc25A and Cdc25B in mitotic cells. Phosphorylation of the RSK sites in these Cdc25 isoforms increases their M-phase-inducing activities. Inhibition of RSK-mediated phosphorylation of Cdc25 inhibits G2/M transition. Moreover, RSK is likely to be more active in mitotic cells than in interphase cells, as evidenced by the phosphorylation status of T359/S363 in RSK. Together, these findings indicate that RSK promotes G2/M transition in mammalian cells through activating phosphorylation of Cdc25A and Cdc25B.

SUBMITTER: Wu CF

PROVIDER: S-EPMC4026278 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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RSK promotes G2/M transition through activating phosphorylation of Cdc25A and Cdc25B.

Wu C F CF Liu S S Lee Y-C YC Wang R R Sun S S Yin F F Bornmann W G WG Yu-Lee L-Y LY Gallick G E GE Zhang W W Lin S-H SH Kuang J J

Oncogene 20130527 18

Activation of the mitogen-activated protein kinase (MAPK) cascade in mammalian cell lines positively regulates the G2/M transition. The molecular mechanism underlying this biological phenomenon remains poorly understood. Ribosomal S6 kinase (RSK) is a key downstream element of the MAPK cascade. Our previous studies established roles of RSK2 in Cdc25C activation during progesterone-induced meiotic maturation of Xenopus oocytes. In this study we demonstrate that both recombinant RSK and endogenous ...[more]

PMID: 23708659

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Project description:PurposeThe aim of this work was to investigate the clinicopathological significance of fibrinogen gamma chain (FGG) and its biological roles during hepatocellular carcinoma (HCC) development and progression.MethodsThe expression of FGG was examined by Western blot and reverse transcription quantitative PCR in two different sample sets, including 24 or 35 pairs of HCC tumor tissues and their corresponding adjacent non-tumorous tissues. Afterward, association analysis between the expression of FGG and clinicopathological characteristics was systematically analyzed in 79 HCC patients. Subsequently, the mobility and invasiveness of SK-HEP-1 cells with FGG overexpression or knockdown were evaluated by transwell assay and wound healing assay. Additionally, the expressions of epithelial to mesenchymal transition (EMT)-associated markers were also detected in FGG overexpressed or silenced SK-HEP-1 cells.ResultsThe expression of FGG was significantly increased in primary HCC tissues comparing with its corresponding adjacent non-tumorous tissues. Clinical pathological analysis demonstrated that upregulation of intracellular FGG was significantly associated with increased vascular invasion, more satellite nodules, and more advanced TNM stage, and HCC patients with stronger expression of FGG had a higher recurrence rate and correspondingly a shorter overall survival time. Meanwhile, the high expression of FGG was also proved to be an independent risk factor for disease-free survival after surgical resection. In vitro phenotype studies showed that overexpression of FGG could promote the migration and invasion in SK-HEP-1 cells; conversely, these phenotypes could be significantly inhibited by knocking down the expression of FGG. Mechanism studies indicated that FGG could promote the migration and invasion through EMT signaling pathway by regulating the expressions of Slug and ZEB1.ConclusionFGG played important roles in enhancing cancer cell motility and invasiveness through EMT signaling, and might serve as a potential prognostic biomarker for HCC patients.

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RSK promotes G2/M transition through activating phosphorylation of Cdc25A and Cdc25B.

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RSK promotes G2/M transition through activating phosphorylation of Cdc25A and Cdc25B.

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