title: Polyamine depletion increases cytoplasmic levels of RNA-binding protein HuR leading to stabilization of nucleophosmin and p53 mRNAs.
abstract: Polyamines are essential for maintaining normal intestinal epithelial integrity, an effect that relies, at least in part, on their ability to keep low levels of nucleophosmin (NPM) and p53 mRNAs. The RNA-binding protein HuR associates with the p53 mRNA, as reported previously, and with the NPM mRNA, computationally predicted to be a target of HuR. Here, we show that HuR binds the NPM and p53 3'-untranslated regions and stabilizes these mRNAs in polyamine-depleted intestinal epithelial cells. Depletion of cellular polyamines by inhibiting ornithine decarboxylase with alpha-difluoromethylornithine dramatically enhanced the cytoplasmic abundance of HuR, whereas ectopic ornithine decarboxylase overexpression decreased cytoplasmic HuR; neither intervention changed whole-cell HuR levels. HuR was found to specifically bind the 3'-untranslated regions of NPN and p53 mRNAs. HuR silencing rendered the NPM and p53 mRNAs unstable and prevented increases in NPM and p53 mRNA and protein in polyamine-deficient cells. These results indicate that polyamines modulate cytoplasmic HuR levels in intestinal epithelial cells, in turn controlling the stability of the NPM and p53 mRNAs and influencing NPM and p53 protein levels.
authors.affiliation: Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore 21201, USA.
authors.forename: Tongtong
authors.initials: T
authors.lastname: Zou
authors.forename: Krystyna
authors.initials: K
authors.lastname: Mazan-Mamczarz
authors.forename: Jaladanki N
authors.initials: JN
authors.lastname: Rao
authors.forename: Lan
authors.initials: L
authors.lastname: Liu
authors.forename: Bernard S
authors.initials: BS
authors.lastname: Marasa
authors.forename: Ai-Hong
authors.initials: AH
authors.lastname: Zhang
authors.forename: Lan
authors.initials: L
authors.lastname: Xiao
authors.forename: Rudolf
authors.initials: R
authors.lastname: Pullmann
authors.forename: Myriam
authors.initials: M
authors.lastname: Gorospe
authors.forename: Jian-Ying
authors.initials: JY
authors.lastname: Wang
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D000954:Antigens, Surface / Q000502:physiology*; D001483:Base Sequence; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; D000518:Eflornithine / Q000737:chemistry; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry*; D000090243:Nucleophosmin; D009955:Ornithine Decarboxylase / Q000737:chemistry; D011073:Polyamines / Q000737:chemistry*; D011485:Protein Binding; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000502:physiology; D051381:Rats; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism / Q000502:physiology*
chemical_list: D020413:3' Untranslated Regions; D000954:Antigens, Surface; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; C098770:ELAVL1 protein, human; C000716967:NPM1 protein, human; D009687:Nuclear Proteins; D011073:Polyamines; D016601:RNA-Binding Proteins; D016159:Tumor Suppressor Protein p53; D000090243:Nucleophosmin; D009955:Ornithine Decarboxylase; D000518:Eflornithine