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MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS
1Institut National de la Santé et de la Recherche Médicale U467, Faculté de Médecine Necker, Université René Descartes Paris V, Paris; and 2Institut National de la Santé et de la Recherche Médicale U468, Université Paris XII, Hôpital H. Mondor, Creteil, France
Submitted 6 December 2004 ; accepted in final form 6 June 2005
Expression of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene, which contains the mutations responsible for CF, is regulated by cytokines (TNF-
and IL-1
) in a cell-specific manner. TNF-
decreases CFTR mRNA in human colon cell lines (HT-29), but not in pulmonary cell lines (Calu-3), and IL-1
increases it only in Calu-3 cells. We looked for the cytokine-induced posttranscriptional regulation of CFTR gene expression and studied the modulation of CFTR mRNA stability linked to its 3' untranslated sequence (3'UTR) in HT-29 and Calu-3 cells. The stability of CFTR mRNA was analyzed by Northern blot after in vitro incubation of total RNAs from CFTR-expressing cells with cytosolic proteins extracted from control or cytokine-treated HT-29 and Calu-3 cells. CFTR mRNA was degraded only by extracts of TNF-
-treated HT-29 cells and not by cytosolic proteins from untreated or IL-1
-treated HT-29 cells. In contrast, extracts of untreated Calu-3 cells enhanced CFTR mRNA degradation, and IL-1
treatment inhibited this; TNF-
had no significant effect. The 3'UTR part of CFTR mRNA was found to be required for this posttranscriptional regulation. The 5' part of the 3'UTR (the 217 first bases), which contains two AUUUA sequences, was implicated in CFTR mRNA destabilization and the following 136 bases, containing several C-repeats in U-rich environment, in its protection. The proteins, which reacted with the U- and C-repeats of CFTR mRNA 3'UTR, were mainly controlled by stimulation of the p42/p44 and p38 MAP kinase cascades with interaction between these pathways. This posttranscriptional control of gene expression is a common feature of CFTR and many proteins of inflammation.
cytokines; HT-29; Calu-3
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