Marshall Renée M, Salerno Dominic, Garriga Judit, Graña Xavier
Fels Institute for Cancer Research and Molecular Biology and Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA.
J Immunol. 2005 Nov 15;175(10):6402-11. doi: 10.4049/jimmunol.175.10.6402.
Stimulation of primary human T lymphocytes results in up-regulation of cyclin T1 expression, which correlates with phosphorylation of the C-terminal domain of RNA polymerase II (RNAP II). Up-regulation of cyclin T1 and concomitant stabilization of cyclin-dependent kinase 9 (CDK9) may facilitate productive replication of HIV in activated T cells. We report that treatment of PBLs with two mitogens, PHA and PMA, results in accumulation of cyclin T1 via distinct mechanisms. PHA induces accumulation of cyclin T1 mRNA and protein, which results from cyclin T1 mRNA stabilization, without significant change in cyclin T1 promoter activity. Cyclin T1 mRNA stabilization requires the activation of both calcineurin and JNK because inhibition of either precludes cyclin T1 accumulation. In contrast, PMA induces cyclin T1 protein up-regulation by stabilizing cyclin T1 protein, apparently independently of the proteasome and without accumulation of cyclin T1 mRNA. This process is dependent on Ca2+-independent protein kinase C activity but does not require ERK1/2 activation. We also found that PHA and anti-CD3 Abs induce the expression of both the cyclin/CDK complexes involved in RNAP II C-terminal domain phosphorylation and the G1-S cyclins controlling cell cycle progression. In contrast, PMA alone is a poor inducer of the expression of G1-S cyclins but often as potent as PHA in inducing RNAP II cyclin/CDK complexes. These findings suggest coordination in the expression and activation of RNAP II kinases by pathways that independently stimulate gene expression but are insufficient to induce S phase entry in primary T cells.
对原代人T淋巴细胞的刺激导致细胞周期蛋白T1表达上调，这与RNA聚合酶II（RNAP II）C末端结构域的磷酸化相关。细胞周期蛋白T1的上调和细胞周期蛋白依赖性激酶9（CDK9）的同时稳定可能促进HIV在活化T细胞中的有效复制。我们报告，用两种促有丝分裂原PHA和PMA处理外周血淋巴细胞（PBLs），通过不同机制导致细胞周期蛋白T1的积累。PHA诱导细胞周期蛋白T1 mRNA和蛋白的积累，这是由于细胞周期蛋白T1 mRNA的稳定化，而细胞周期蛋白T1启动子活性没有显著变化。细胞周期蛋白T1 mRNA的稳定化需要钙调神经磷酸酶和JNK的激活，因为对其中任何一种的抑制都会阻止细胞周期蛋白T1的积累。相反，PMA通过稳定细胞周期蛋白T1蛋白诱导细胞周期蛋白T1蛋白上调，显然独立于蛋白酶体且细胞周期蛋白T1 mRNA没有积累。这个过程依赖于不依赖Ca2+的蛋白激酶C活性，但不需要ERK1/2激活。我们还发现，PHA和抗CD3抗体诱导参与RNAP II C末端结构域磷酸化的细胞周期蛋白/CDK复合物以及控制细胞周期进程的G1-S细胞周期蛋白的表达。相比之下，单独的PMA是G1-S细胞周期蛋白表达的弱诱导剂，但在诱导RNAP II细胞周期蛋白/CDK复合物方面通常与PHA一样有效。这些发现表明，通过独立刺激基因表达但不足以诱导原代T细胞进入S期的途径，在RNAP II激酶的表达和激活中存在协调作用。
