Chronic Ethanol Exposure Increases the Binding of HuR to the TNFα 3â²-Untranslated Region in Macrophages
Tumor necrosis factor α (TNFα) expression is a key mediator of ethanol-induced liver disease. Increased lipopolysaccharide (LPS)-stimulated TNFα expression in macrophages after chronic ethanol feeding is associated with a stabilization of TNFα mRNA (Kishore, R., McMullen, M. R., and Nagy, L. E....
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Published in | The Journal of biological chemistry Vol. 278; no. 40; p. 38333 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
American Society for Biochemistry and Molecular Biology
03.10.2003
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Online Access | Get full text |
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Summary: | Tumor necrosis factor α (TNFα) expression is a key mediator of ethanol-induced liver disease. Increased lipopolysaccharide
(LPS)-stimulated TNFα expression in macrophages after chronic ethanol feeding is associated with a stabilization of TNFα mRNA
(Kishore, R., McMullen, M. R., and Nagy, L. E. (2001) J. Biol. Chem. 276, 41930â41937). Here we show that the 3â²-UTR of murine TNFα mRNA was sufficient to mediate increased LPS-stimulated expression
of a luciferase reporter in RAW 264.7 macrophages after chronic ethanol exposure. Further, we show that HuR, a nuclear/cytoplasmic
shuttling protein, which binds to TNFα mRNA, is required for increased expression of TNFα after chronic ethanol. In Kupffer
cells, HuR was primarily localized to the nucleus and then translocated to the cytosol in response to LPS in both pair- and
ethanol-fed rats. After chronic ethanol feeding, HuR quantity in the cytosol was greater, both at baseline and in response
to LPS, compared with pair-fed controls. Using RNA gel shift assays, we found that LPS treatment increased HuR binding to
the 65-nucleotide A + U-rich element of the TNFα 3â²-UTR by 2-fold over baseline in Kupffer cells from pair-fed rats. After
chronic ethanol feeding, HuR binding to the TNFα A + U-rich element was increased by more than 5-fold at baseline and in response
to LPS, compared with pair-fed controls. Down-regulation of HuR expression by RNA interference prevented the chronic ethanol-induced
increase in expression of luciferase reporters containing the TNFα 3â²-UTR. Taken together, these data demonstrate that increased
binding of HuR to the TNFα 3â²-UTR contributes to increased LPS-stimulated TNFα expression in macrophages after chronic ethanol
exposure. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M304566200 |