Phosphorylation of the UL31 Protein of Herpes Simplex Virus 1 by the US3-Encoded Kinase Regulates Localization of the Nuclear Envelopment Complex and Egress of Nucleocapsids
Phosphorylation of the UL31 Protein of Herpes Simplex Virus 1 by the US3-Encoded Kinase Regulates Localization of the Nuclear Envelopment Complex and Egress of Nucleocapsids
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DOI：
10.1128/jvi.00090-09
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发表时间：
2009-05-15
影响因子：
5.4
通讯作者：
Baines, Joel D.
中科院分区：
文献类型：
--
作者：
Mou, Fan;Wills, Elizabeth;Baines, Joel D.
单纯疱疹病毒1型核衣壳通过内核膜（INM）出芽进入核周间隙以获得初级病毒包膜。这一过程需要在内核膜处由U(L)31和U(L)34基因产物组成的蛋白质复合物。虽然很明显由U(S)3基因编码的病毒激酶调节pU(L)31 / pU(L)34在内核膜内的定位，但实现这一过程的分子机制仍然是个谜。在此，我们确定了以下几点。（i）pU(L)31的N末端对该蛋白质的正常功能是必不可少的，并且包含多达六个在感染过程中被US3激酶磷酸化的丝氨酸。（ii）这六个丝氨酸的磷酸化对于有效感染不是必需的，但对于最佳的病毒生长动力学是必需的。（iii）在有活性的U(S)3激酶存在的情况下，将丝氨酸变为丙氨酸会导致pUL31 / pUL34复合物在核边缘聚集，并导致一些病毒粒子异常地聚集在核膜的疝出部位，这与感染U(S)3激酶失活突变体的细胞情况非常相似。（iv）用谷氨酸替代pUL31的六个丝氨酸在很大程度上恢复了pU(L)34 / pU(L)31在核膜上的平滑分布，并且无论U(S)3激酶是否有活性，都阻止了病毒粒子在疝出部位的聚集，但也阻止了核衣壳的最佳初级包膜形成。这些观察结果表明，pU(S)3对pU(L)31的磷酸化是病毒粒子释放途径中的一个重要调节事件，这可以解释pU(S)3在核释放过程中的大部分作用。数据还表明，pU(L)31磷酸化的动力学既调节初级包膜形成，也调节新生病毒粒子包膜与外核膜随后的融合。
Herpes simplex virus 1 nucleocapsids bud through the inner nuclear membrane (INM) into the perinuclear space to obtain a primary viral envelope. This process requires a protein complex at the INM composed of the U(L)31 and U(L)34 gene products. While it is clear that the viral kinase encoded by the U(S)3 gene regulates the localization of pU(L)31/pU(L)34 within the INM, the molecular mechanism by which this is accomplished remains enigmatic. Here, we have determined the following. (i) The N terminus of pU(L)31 is indispensable for the protein's normal function and contains up to six serines that are phosphorylated by the US3 kinase during infection. (ii) Phosphorylation at these six serines was not essential for a productive infection but was required for optimal viral growth kinetics. (iii) In the presence of active U(S)3 kinase, changing the serines to alanine caused the pUL31/pUL34 complex to aggregate at the nuclear rim and caused some virions to accumulate aberrantly in herniations of the nuclear membrane, much as in cells infected with a U(S)3 kinase-dead mutant. (iv) The replacement of the six serines of pUL31 with glutamic acid largely restored the smooth distribution of pU(L)34/pU(L)31 at the nuclear membrane and precluded the accumulation of virions in herniations whether or not U(S)3 kinase was active but also precluded the optimal primary envelopment of nucleocapsids. These observations indicate that the phosphorylation of pU(L)31 by pU(S)3 represents an important regulatory event in the virion egress pathway that can account for much of pU(S)3's role in nuclear egress. The data also suggest that the dynamics of pU(L)31 phosphorylation modulate both the primary envelopment and the subsequent fusion of the nascent virion envelope with the outer nuclear membrane.