Alternative splicing factor/splicing factor 2 regulates the expression of the zeta subunit of the human T cell receptor-associated CD3 complex.
T cells from patients with systemic lupus erythematosus express decreased levels of the T cell receptor-associated CD3 zeta chain, a feature directly linked to their aberrant function. The decrease in CD3zeta protein expression is in part due to decreased levels of functional wild type isoform of the 3'-untranslated region (UTR) of CD3zeta mRNA with concomitant increased levels of an unstable alternatively spliced isoform. In order to identify factors involved in the post-transcriptional regulation of CD3zeta, we performed mass spectrometric analysis of Jurkat T cell nuclear proteins "pulled down" by a CD3zeta 3'-UTR oligonucleotide, which identified the splicing protein alternative splicing factor/splicing factor 2 (ASF/SF2). We show for the first time that ASF/SF2 binds specifically to the 3'-UTR of CD3zeta and regulates expression of CD3zeta protein by limiting the production of the alternatively spliced isoform. During activation of human T cells, an increase in the wild type CD3zeta mRNA is associated with increased expression of ASF/SF2. Finally, we show a significant correlation between ASF/SF2 and CD3zeta protein levels in T cells from systemic lupus erythematosus patients. Thus, our results identify ASF/SF2 as a novel factor in the regulation of alternative splicing of the 3'-UTR of CD3zeta and protein expression in human T cells.
Moulton
Vaishali R
VR
Division of Rheumatology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115, USA.
Tsokos
George C
GC
D020413:3' Untranslated Regions; D017398:Alternative Splicing; D017252:CD3 Complex / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D019169:Jurkat Cells; D008180:Lupus Erythematosus, Systemic / Q000378:metabolism*; D008297:Male; D009687:Nuclear Proteins / Q000378:metabolism*; D020033:Protein Isoforms / Q000096:biosynthesis; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors; D013601:T-Lymphocytes / Q000378:metabolism*
D020413:3' Untranslated Regions; D017252:CD3 Complex; C121704:CD3 antigen, zeta chain; D009687:Nuclear Proteins; D020033:Protein Isoforms; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors