The zeta subunit of the T cell antigen receptor (TCR) exists primarily as a disulfide-linked homodimer. This receptor subunit is important in TCR-mediated signal transduction and is a substrate for a TCR-activated protein tyrosine kinase. The zeta chain was found to undergo ubiquitination in response to receptor engagement. This posttranslational modification occurred in normal T cells and tumor lines. Both nonphosphorylated and phosphorylated zeta molecules were modified, and at least one other TCR subunit, CD3 delta, was also ubiquitinated after activation of the receptor. These findings suggest an expanded role for ubiquitination in transmembrane receptor function.

Objective. We have recently found that the presence of autoantibodies against the 70-kd polypeptide of U1 RNP (Ul-70-kd) is associated with HLA-DR4 and DR2. To further characterize this association, we performed a molecular genetic analysis of HLA-DR and DQ genes among patients with autoantibodies against Methods. The polymerase chain reaction (PCR), sequence-specific oligonucleotide hybridization, and U1-70-kd.

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0401 is associated with the presence of autoantibodies reactive with the U1-70 kD polypeptide antigen of U 1 -small nuclear ribonucleoprotein among connective tissue disease patients, Tissue Antigens 1992: 39: 212-275.Systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD) are characterized by the frequent presence of autoantibodies reactive with specific uridine-rich RNA-small nuclear ribonucleoproteins complexes (snRNP), including the Sm and RNP antigens. Among such patients, we have recently demonstrated an association between the presence of either HLA-DR4 or HLA-DR2 with autoantibodies reactive with a specific antigen of the snRTW complex, the U1-70 kD polypeptide (1, 2). The purpose of the present study was to determine whether HLA-DP was associated with the presence of autoantibodies reactive with individual snRNP polypeptide antigens and to map more completely the region within the human major histocompatibility complex which contributes to the association of HLA with autoantibody production.