title: Post-transcriptional regulation of MEK-1 by polyamines through the RNA-binding protein HuR modulating intestinal epithelial apoptosis.
abstract: MEK-1 [MAPK (mitogen-activated protein kinase) kinase-1] is an important signal transducing enzyme that is implicated in many aspects of cellular functions. In the present paper, we report that cellular polyamines regulate MEK-1 expression at the post-transcriptional level through the RNA-binding protein HuR (Hu-antigen R) in IECs (intestinal epithelial cells). Decreasing the levels of cellular polyamines by inhibiting ODC (ornithine decarboxylase) stabilized MEK-1 mRNA and promoted its translation through enhancement of the interaction between HuR and the 3'-untranslated region of MEK-1 mRNA, whereas increasing polyamine levels by ectopic ODC overexpression destabilized the MEK-1 transcript and repressed its translation by reducing the abundance of HuR-MEK-1 mRNA complex; neither intervention changed MEK-1 gene transcription via its promoter. HuR silencing rendered the MEK-1 mRNA unstable and inhibited its translation, thus preventing increases in MEK-1 mRNA and protein in polyamine-deficient cells. Conversely, HuR overexpression increased MEK-1 mRNA stability and promoted its translation. Inhibition of MEK-1 expression by MEK-1 silencing or HuR silencing prevented the increased resistance of polyamine-deficient cells to apoptosis. Moreover, HuR overexpression did not protect against apoptosis if MEK-1 expression was silenced. These results indicate that polyamines destabilize the MEK-1 mRNA and repress its translation by inhibiting the association between HuR and the MEK-1 transcript. Our findings indicate that MEK-1 is a key effector of the HuR-elicited anti-apoptotic programme in IECs.
authors.affiliation: Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
authors.forename: Peng-Yuan
authors.initials: PY
authors.lastname: Wang
authors.forename: Jaladanki N
authors.initials: JN
authors.lastname: Rao
authors.forename: Tongtong
authors.initials: T
authors.lastname: Zou
authors.forename: Lan
authors.initials: L
authors.lastname: Liu
authors.forename: Lan
authors.initials: L
authors.lastname: Xiao
authors.forename: Ting-Xi
authors.initials: TX
authors.lastname: Yu
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Turner
authors.forename: Myriam
authors.initials: M
authors.lastname: Gorospe
authors.forename: Jian-Ying
authors.initials: JY
authors.lastname: Wang
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis; D001483:Base Sequence; D015153:Blotting, Western; D002460:Cell Line; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D015971:Gene Expression Regulation, Enzymologic; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000473:pathology; D048369:MAP Kinase Kinase 1 / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011073:Polyamines / Q000378:metabolism*; D014176:Protein Biosynthesis; D034622:RNA Interference; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic
chemical_list: D000954:Antigens, Surface; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; C098770:ELAVL1 protein, human; D011073:Polyamines; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D048369:MAP Kinase Kinase 1