Binding of the ELAV-like protein in murine autoimmune T-cells to the nonameric AU-rich element in the 3' untranslated region of CD154 mRNA.

The CD154 molecule is important for experimental allergic encephalomyelitis (EAE) which is mediated by autoimmune CD4(+) T-cells. Post-transcriptional instabilization/stabilization of mRNAs, which contain an adenylate uridylate rich element (ARE) in their 3' untranslated region (3'UTR), is regulated in part by binding of ARE-binding proteins to the element. We have investigated the protein which binds to the nonameric ARE in the 3'UTR of CD154 mRNA. A protein which binds to the CD154 ARE was found to exist in a extract prepared from murine autoimmune T-cells activated with myelin basic protein (MBP), and turned out to be mHuR which is a ubiquitous ELAV-like protein. It was found that mHuR was upregulated upon stimulation of the T-cells with a MBP antigen. The CD154 ARE and the ARE in the 3'UTR of tumor necrosis factor-alpha (TNF-alpha) mRNA were competed in binding to mHuR, indicating that both AREs bind to the same site on mHuR. The presence of the CD154 ARE downstream of the luciferase cDNA in a reporter plasmid decreased the translational efficiency, and co-expression of the mHuR slightly increased the translation. These results suggest the possibility that the ELAV-like protein participates in the regulation of the expression of CD154 on the autoimmune T-cells. Modification of the expression of CD154 on autoimmune T-cells by regulating the ELAV-like protein may provide effective therapy for EAE and human multiple sclerosis.