Decreased Stability and Translation of T Cell Receptor ζ mRNA with an Alternatively Spliced 3′-Untranslated Region Contribute to ζ Chain Down-regulation in Patients with Systemic Lupus Erythematosus

The molecular mechanisms involved in the aberrant expression of T cell receptor (TCR) ζ chain of patients with systemic lupus erythematosus are not known. Previously we demonstrated that although normal T cells express high levels of TCR ζ mRNA with wild-type (WT) 3′ untranslated region (3′ UTR), systemic lupus erythematosus T cells display significantly high levels of TCR ζ mRNA with the alternatively spliced (AS) 3′ UTR form, which is derived by splice deletion of nucleotides 672–1233 of the TCR ζ transcript. Here we report that the stability of TCR ζ mRNA with an AS 3′ UTR is low compared with TCR ζ mRNA with WT 3′ UTR. AS 3′ UTR, but not WT 3′ UTR, conferred similar instability to the luciferase gene. Immunoblotting of cell lysates derived from transfected COS-7 cells demonstrated that TCR ζ with AS 3′ UTR produced low amounts of 16-kDa protein. In vitro transcription and translation also produced low amounts of protein from TCR ζ with AS 3′ UTR. Taken together our findings suggest that nucleotides 672–1233 bp of TCR ζ 3′ UTR play a critical role in its stability and also have elements required for the translational regulation of TCR ζ chain expression in human T cells.