Feuerstein N, Firestein R, Aiyar N, He X, Murasko D, Cristofalo V
Center for Gerontologic Research, Medical College of Pennsylvania and Hahnemann University, Philadelphia, PA 19129, USA.
J Immunol. 1996 Jun 15;156(12):4582-93.
Transcription factors of the cAMP-responsive element (CRE) binding protein/activating transcription factor (CREB/ATF) family were implicated in the expression of T cell-specific genes and in the expression of oncogenic retroviruses associated with leukemia in T and B lymphocytes. To study the regulation of CREB/ATF transcription factors during lymphocyte activation, studies were pursued in primary cultures of resting murine splenic T and B lymphocytes stimulated via the Ag receptor. Using consensus/CRE and proliferating cell nuclear Ag (PCNA)/CRE as probes in the DNA binding assay, we showed that a marked induction of CRE binding is associated with activation of splenic T lymphocytes with anti-CD3 Ab. CRE binding was markedly induced after 48 h; it gradually declined at 72 h, but remained elevated above control levels after 120 h. Most significant, activation by anti-CD3 was associated with a marked induction of cAMP levels that preceded the onset of DNA synthesis and the induction of IL-2 secretion and reached a peak after 48 h (9.5- to 11-fold), concomitant with the peak in CRE binding. Rapamycin, a potent immunosuppressant, inhibited the induction of cAMP levels by anti-CD3 concomitant with inhibition of CRE binding activity and arrest of DNA synthesis. A marked induction in CRE binding after 48 h was also found in splenic B lymphocytes stimulated by LPS and anti-Ig and was correlated with a 3- to 4-fold increase in the intracellular levels of cAMP. Two inducible CRE complexes were found to bind to consensus/CRE and PCNA/CRE; the major complex contained primarily CREB homodimers and was constitutively expressed in resting lymphocytes. Conversely, stimulation of lymphocytes was associated with formation of a new, slow migrating CRE complex that demonstrated high inducibility in both consensus/CRE and PCNA/CRE. We show that this de novo inducible CRE complex contains CREB and ATF2, but not ATF1. Taken collectively, these results suggest that recruitment of CREB and ATF2 to the promoter of genes is tightly regulated during activation of T and B lymphocytes and implicate a cross-talk of cAMP and non-cAMP pathways in the regulation of transcriptional processes at late stages of activation in T and B lymphocytes stimulated via the Ag receptor.
环磷酸腺苷反应元件（CRE）结合蛋白/激活转录因子（CREB/ATF）家族的转录因子与T细胞特异性基因的表达以及T和B淋巴细胞中与白血病相关的致癌逆转录病毒的表达有关。为了研究淋巴细胞激活过程中CREB/ATF转录因子的调控，我们对通过抗原受体刺激的静息小鼠脾T和B淋巴细胞原代培养物进行了研究。在DNA结合试验中使用共有序列/CRE和增殖细胞核抗原（PCNA）/CRE作为探针，我们发现CRE结合的显著诱导与抗CD3抗体激活脾T淋巴细胞有关。48小时后CRE结合显著诱导；72小时时逐渐下降，但120小时后仍高于对照水平。最显著的是，抗CD3激活与DNA合成开始前cAMP水平的显著诱导以及IL-2分泌的诱导有关，并在48小时后达到峰值（9.5至11倍），与CRE结合的峰值同时出现。雷帕霉素是一种强效免疫抑制剂，它抑制抗CD3诱导的cAMP水平，同时抑制CRE结合活性并阻止DNA合成。在LPS和抗Ig刺激的脾B淋巴细胞中也发现48小时后CRE结合显著诱导，并且与细胞内cAMP水平增加3至4倍相关。发现有两种可诱导的CRE复合物与共有序列/CRE和PCNA/CRE结合；主要复合物主要包含CREB同二聚体，在静息淋巴细胞中组成性表达。相反，淋巴细胞刺激与一种新的、迁移缓慢的CRE复合物形成有关，该复合物在共有序列/CRE和PCNA/CRE中均表现出高诱导性。我们表明这种从头诱导的CRE复合物包含CREB和ATF2，但不包含ATF1。总体而言，这些结果表明在T和B淋巴细胞激活过程中，CREB和ATF2募集到基因启动子受到严格调控，并暗示在通过抗原受体刺激的T和B淋巴细胞激活后期的转录过程调控中，cAMP和非cAMP途径存在相互作用。
