McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin School of Medicine and Public Health, 1400 University Ave., Madison, WI 53706, USA.
J Virol. 2010 May;84(9):4383-94. doi: 10.1128/JVI.02369-09. Epub 2010 Feb 24.
The Epstein-Barr virus (EBV) immediate-early protein BZLF1 (Z) mediates the switch between latent and lytic EBV infection. Z not only activates early lytic viral gene transcription but also plays a direct role in lytic viral genome replication. Although a small fraction of Z is known to be sumoylated, the effects of this posttranslational modification on various different Z functions have not been well defined. In this report, we show that only the lysine at amino acid residue 12 is required for the sumoylation of Z, and that Z can be sumoylated by SUMO isoforms 1, 2, and 3. We also demonstrate that the sumo-defective Z mutants ZK12A and ZK12R have enhanced transcriptional activity. The sumoylated and nonsumoylated forms of Z were found to have a similar cellular location, both being localized primarily within the nuclear matrix. The Z sumo-defective mutants were, however, partially defective for disrupting promyelocytic leukemia (PML) bodies compared to the ability of wild-type Z. In addition, we show that lytic viral genome replication does not require the sumoylation of Z, although a Z mutant altered at both amino acids 12 and 13 is replication defective. Furthermore, we show that the sumoylation of Z is greatly increased (from less than 1 to about 11%) in lytically induced 293 cells infected with an EBV mutant virus deleted for the EBV-encoded protein kinase (EBV-PK) compared to that of 293 cells infected with wild-type EBV, and that the overexpression of EBV-PK leads to the reduced sumoylation of Z in EBV-negative cells. Our results suggest that the sumoylation of Z helps to promote viral latency, and that EBV-PK inhibits Z sumoylation during viral reactivation.
EBV 立即早期蛋白 BZLF1（Z）介导潜伏和裂解 EBV 感染之间的转换。Z 不仅激活早期裂解病毒基因转录，而且在裂解病毒基因组复制中发挥直接作用。虽然已知 Z 的一小部分被 SUMO 化，但这种翻译后修饰对各种不同 Z 功能的影响尚未得到很好的定义。在本报告中，我们表明只有氨基酸残基 12 上的赖氨酸是 Z 发生 SUMO 化所必需的，并且 Z 可以被 SUMO 同种型 1、2 和 3 进行 SUMO 化。我们还证明，SUMO 缺陷型 Z 突变体 ZK12A 和 ZK12R 具有增强的转录活性。SUMO 化和非 SUMO 化形式的 Z 被发现具有相似的细胞定位，两者主要位于核基质内。与野生型 Z 相比，SUMO 缺陷型 Z 突变体在破坏早幼粒细胞白血病（PML）体方面仅部分缺陷。此外，我们表明裂解病毒基因组复制不需要 Z 的 SUMO 化，尽管在氨基酸 12 和 13 处均发生突变的 Z 突变体是复制缺陷的。此外，我们表明，与感染野生型 EBV 的 293 细胞相比，在感染缺失 EBV 编码蛋白激酶（EBV-PK）的 EBV 突变病毒的裂解诱导的 293 细胞中，Z 的 SUMO 化大大增加（从少于 1%增加到约 11%），并且 EBV-PK 的过表达导致 EBV 阴性细胞中 Z 的 SUMO 化减少。我们的结果表明，Z 的 SUMO 化有助于促进病毒潜伏，并且 EBV-PK 在病毒重新激活期间抑制 Z 的 SUMO 化。
