T-cell receptor < zeta > mRNA with an alternatively spliced 3' untranslated region is generated predominantly in the peripheral blood T cells of systemic lupus erythematosus patients

摘要

To investigate the mechanism of the downregulation of T-cell receptor < zeta > chain (TCR< zeta >) expression in the peripheral blood T cells (PBTs) of systemic lupus erythematosus (SLE) patients, we analyzed the 3' untranslated region (3'UTR) of TCR< zeta > mRNA, because the 3'UTR in mRNA is responsible for posttranscriptional regulation. Use of the reverse transcriptase polymerase chain reaction (RT-PCR) to amplify the 917bp TCR< zeta > 3'UTR cDNA demonstrated that the short variant cDNA (355bp), expressed as an alternatively spliced 3'UTR with 562-bp deletion, was predominated in the PBTs of 11 of 14 SLE patients, whereas mainly the wild-form cDNA (917bp) was detected in the PBTs of seven negative controls (two systemic sclerosis patients, five normal controls) and in two T-cell line hybridomas. Semiquantitative PCR also revealed the predominant expression of the TCR< zeta > mRNA with alternatively spliced 3'UTR (TCR< zeta > mRNA/as-3'UTR), and a decreased expression of TCR< zeta > mRNA with the wild form 3'UTR (TCR< zeta > mRNA/w-3'UTR) in SLE T cells. However, there was no difference in the expression of the open reading frame (ORF) TCR< zeta > mRNA between the negative controls and SLE patients. The TCR< zeta > protein expression level according to Western blot analysis correlated well with that of TCR< zeta > mRNA/w-3'UTR (r = 0.931) and reversibly with TCR< zeta > mRNA/as-3'UTR (r = -0.614), but not with ORF TCR< zeta > mRNA (r = -0.296). It can be concluded that the reduced expression of TCR< zeta > mRNA/w-3'UTR and the pre-dominant expression of TCR< zeta > mRNA/as-3'UTR lead to downregulation of the TCR< zeta > protein in SLE T cells.