Domingues Rita G, Lago-Baldaia Inês, Pereira-Castro Isabel, Fachini Joseph M, Oliveira Liliana, Drpic Danica, Lopes Nair, Henriques Telmo, Neilson Joel R, Carmo Alexandre M, Moreira Alexandra
Gene Regulation Group, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Portugal.
Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal.
Eur J Immunol. 2016 Jun;46(6):1490-503. doi: 10.1002/eji.201545663. Epub 2016 Apr 15.
T lymphocytes stimulated through their antigen receptor (TCR) preferentially express mRNA isoforms with shorter 3´ untranslated regions (3´-UTRs) derived from alternative pre-mRNA cleavage and polyadenylation (APA). However, the physiological relevance of APA programs remains poorly understood. CD5 is a T-cell surface glycoprotein that negatively regulates TCR signaling from the onset of T-cell activation. CD5 plays a pivotal role in mediating outcomes of cell survival or apoptosis, and may prevent both autoimmunity and cancer. In human primary T lymphocytes and Jurkat cells we found three distinct mRNA isoforms encoding CD5, each derived from distinct poly(A) signals (PASs). Upon T-cell activation, there is an overall increase in CD5 mRNAs with a specific increase in the relative expression of the shorter isoforms. 3´-UTRs derived from these shorter isoforms confer higher reporter expression in activated T cells relative to the longer isoform. We further show that polypyrimidine tract binding protein (PTB/PTBP1) directly binds to the proximal PAS and PTB siRNA depletion causes a decrease in mRNA derived from this PAS, suggesting an effect on stability or poly(A) site selection to circumvent targeting of the longer CD5 mRNA isoform by miR-204. These mechanisms fine-tune CD5 expression levels and thus ultimately T-cell responses.
通过其抗原受体（TCR）刺激的T淋巴细胞优先表达源自替代性前体mRNA切割和多聚腺苷酸化（APA）的具有较短3´非翻译区（3´-UTR）的mRNA亚型。然而，APA程序的生理相关性仍知之甚少。CD5是一种T细胞表面糖蛋白，从T细胞激活开始就对TCR信号传导起负调节作用。CD5在介导细胞存活或凋亡的结果中起关键作用，并可能预防自身免疫和癌症。在人原代T淋巴细胞和Jurkat细胞中，我们发现了三种不同的编码CD5的mRNA亚型，每种都源自不同的聚腺苷酸化信号（PAS）。在T细胞激活后，CD5 mRNA总体增加，较短亚型的相对表达有特定增加。相对于较长亚型，源自这些较短亚型的3´-UTR在活化的T细胞中赋予更高的报告基因表达。我们进一步表明，聚嘧啶序列结合蛋白（PTB/PTBP1）直接结合近端PAS，PTB siRNA缺失导致源自该PAS的mRNA减少，这表明对稳定性或聚腺苷酸化位点选择有影响，以规避miR-204对较长CD5 mRNA亚型的靶向。这些机制微调CD5表达水平，从而最终调节T细胞反应。
