title: Regulation of intercellular adhesion molecule-1 gene expression involves multiple mRNA stabilization mechanisms: effects of interferon-gamma and phorbol myristate acetate.
abstract: Although the intercellular adhesion molecule-1 (ICAM-1) is constitutively expressed at a low level on a subpopulation of hematopoietic cells, on vascular endothelium, on fibroblasts, and on certain epithelial cells, it is dramatically increased at sites of inflammation. Interferon-gamma (IFN-gamma) and phorbol myristate acetate (PMA) are known to increase the expression of ICAM-1 on many cell types. Because both human and murine ICAM-1 mRNAs contain putative destabilizing AUUUA sequences in their 3' untranslated regions (UTRs), we examined the role of mRNA stability in the regulation of ICAM-1 gene expression. The treatment of the murine monocytic cell line P388D1, which constitutively expresses ICAM-1 mRNA at a low level, with IFN-gamma or PMA rapidly enhanced the level of ICAM-1 mRNA and dramatically prolonged its half-life. To determine whether the putative destabilizing sequences are responsible for this effect of IFN-gamma and PMA, fibroblast L cells were transfected with either the full-length ICAM-1 cDNA or a truncated form (ICAM-1 delta 3) lacking the putative destabilizing AUUUA sequences. Although ICAM-1 delta 3 mRNA was more stable than the full-length ICAM-1 mRNA, IFN-gamma treatment induced the accumulation of both mRNA species and prolongation of their half-lives. The transplantation of the ICAM-1 delta 3' UTR into a stable ICAM-2 mRNA rendered it unstable, and it was unresponsive to IFN-gamma. Therefore, the treatment with IFN-gamma stabilizes the otherwise labile ICAM-1 mRNA, but the IFN-gamma-responsive sequence may at least in part reside within the protein coding region. PMA also upregulated ICAM-1 gene expression by mRNA stabilization. However, unlike IFN-gamma, PMA treatment only increased the level of the full-length, but not of the truncated, ICAM-1 mRNA. This shows that the PMA-responsive element is located within the 3'UTR. Furthermore, the effect of PMA on ICAM-1 delta 3 mRNA was recovered by ligating multiple AUUUA sequences derived from a heterologous gene fragment. The stability of this chimeric mRNA and the full-length ICAM-1 mRNA was markedly increased by PMA treatment, indicating that the AUUUA multimers in the 3'UTR are important in the PMA-induced upregulation of ICAM-1 mRNA.
authors.affiliation: Department of Medical Genetics, University of British Columbia, Vancouver, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Ohh
authors.forename: C A
authors.initials: CA
authors.lastname: Smith
authors.forename: C
authors.initials: C
authors.lastname: Carpenito
authors.forename: F
authors.initials: F
authors.lastname: Takei
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004355:Drug Stability; D005786:Gene Expression Regulation / Q000187:drug effects*; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics*; D007371:Interferon-gamma / Q000494:pharmacology*; D007739:L Cells; D051379:Mice; D008969:Molecular Sequence Data; D009000:Monocytes / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014162:Transfection
chemical_list: D012333:RNA, Messenger; D018799:Intercellular Adhesion Molecule-1; D007371:Interferon-gamma; D013755:Tetradecanoylphorbol Acetate