Activation of the Epstein-Barr virus transcription factor BZLF1 by 12-O-tetradecanoylphorbol-13-acetate-induced phosphorylation
Activation of the Epstein-Barr virus transcription factor BZLF1 by 12-O-tetradecanoylphorbol-13-acetate-induced phosphorylation
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DOI：
10.1128/jvi.72.10.8105-8114.1998
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发表时间：
1998-10-01
影响因子：
5.4
通讯作者：
Hammerschmidt, W
中科院分区：
文献类型：
--
作者：
Baumann, M;Mischak, H;Hammerschmidt, W
BZLF1是扩展的AP-1转录因子家族的成员，它与EB病毒早期启动子中特定的BZLF1序列基序结合，并与密切相关的AP-I基序结合。BZLF1的S活性在转录水平上受到调控，也通过蛋白质相互作用和翻译后修饰来调节。佛波酯或免疫球蛋白均通过反式激活BZLF1重新激活潜伏感染的B细胞中的EBV。本文报道佛波酯12-O-十四酰佛波醇-13-乙酸酯(TPA)能进一步诱导BZLF1‘S的活性。诱导发生在转录后水平，依赖于位于BZLF1 DNA结合域的单个丝氨酸残基。这段丝氨酸残基(S186)在体外和体内都被TPA刺激后被蛋白激酶C磷酸化。S186本身的磷酸化在体外干扰了BZLF1的DNA结合亲和力，但对TPA诱导的BZLF1 DNA结合的增加是必需的，凝胶滞留分析和细胞提取物的重建实验表明。在转录报告分析中，S186是TPA激活BZLF1所必需的。据推测，一种尚未确定的细胞因子可以恢复S186磷酸化的BZLF1的DNA结合亲和力，并增强其转录活性，这是诱导EBV生命周期裂解阶段所必需的。
BZLF1 is a member of the extended AP-1 family of transcription factors which binds to specific BZLF1 sequence motifs within early Epstein-Barr virus (EBV) promoters and to closely related AP-I motifs. BZLF1's activity is regulated at the transcriptional level as well as through protein interactions and posttranslational modifications. Phorbol esters or immunoglobulin cross-linking both reactivate EBV from latently infected B cells via transactivation of BZLF1. We report here that the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) is capable of inducing BZLF1's activity even further. The induction occurs at the posttranscriptional level and depends on a single serine residue located in the DNA binding domain of BZLF1. This serine residue (S186) is phosphorylated by protein kinase C in vitro and in vivo after stimulation with TPA. Phosphorylation of S186 per se interferes with the DNA binding affinity of BZLF1 in vitro but is mandatory for TPA-induced increase in DNA binding of BZLF1, as shown in gel retardation assays and reconstruction experiments with cellular extracts. In transcriptional reporter assays, S186 is essential for the activation of BZLF1 by TPA. Presumably, a yet-to-be-identified cellular factor restores the DNA binding affinity and enhances the transcriptional activity of S186-phosphorylated BZLF1, which is required to induce the lytic phase of EBV's life cycle.