Division of Virology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan.
J Biol Chem. 2010 Jul 30;285(31):23925-35. doi: 10.1074/jbc.M109.095356. Epub 2010 Jun 1.
The transition from latent to lytic phases of the Epstein-Barr virus life cycle is triggered by expression of a viral transactivator, BZLF1, that then induces expression of the viral immediate-early and early genes. The BZLF1 protein is post-translationally modified by a small ubiquitin-related modifier-1 (SUMO-1). Here we found that BZLF1 is conjugated at lysine 12 not only by SUMO-1 but also by SUMO-2 and 3. The K12R mutant of BZLF1, which no longer becomes sumoylated, exhibits stronger transactivation than the wild-type BZLF1 in a reporter assay system as well as in the context of virus genome with nucleosomal structures. Furthermore, exogenous supply of a SUMO-specific protease, SENP, caused de-sumoylation of BZLF1 and enhanced BZLF1-mediated transactivation. Immunoprecipitation experiments proved that histone deacetylase 3 preferentially associated with the sumoylated form of BZLF1. Levels of the sumoylated BZLF1 increased as lytic replication progressed. Based on these observations, we conclude that sumoylation of BZLF1 regulates its transcriptional activity through histone modification during Epstein-Barr virus productive replication.
EB 病毒生命周期从潜伏到裂解期的转变是由病毒转录激活物 BZLF1 的表达触发的，BZLF1 随后诱导病毒即刻早期和早期基因的表达。BZLF1 蛋白通过一种小泛素相关修饰物 1（SUMO-1）进行翻译后修饰。在这里，我们发现 BZLF1 在赖氨酸 12 处不仅与 SUMO-1 结合，还与 SUMO-2 和 SUMO-3 结合。BZLF1 的 K12R 突变体不再被 SUMO 化，在报告基因检测系统以及具有核小体结构的病毒基因组中，其转录激活活性比野生型 BZLF1 更强。此外，外源性提供 SUMO 特异性蛋白酶 SENP 会导致 BZLF1 去 SUMO 化，并增强 BZLF1 介导的转录激活。免疫沉淀实验证明组蛋白去乙酰化酶 3 优先与 BZLF1 的 SUMO 化形式结合。随着裂解复制的进行，SUMO 化 BZLF1 的水平增加。基于这些观察结果，我们得出结论，SUMO 化 BZLF1 通过组蛋白修饰来调节其在 EB 病毒有性复制过程中的转录活性。
