The Human Adenovirus Type 5 L4 Promoter Is Negatively Regulated by TFII-I and L4-33K.
The Human Adenovirus Type 5 L4 Promoter Is Negatively Regulated by TFII-I and L4-33K.
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DOI：
10.1128/jvi.00683-15
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发表时间：
2015-07
影响因子：
5.4
通讯作者：
Leppard KN
中科院分区：
文献类型：
--
作者：
Wright J;Atwan Z;Morris SJ;Leppard KN
腺病毒基因表达的晚期由中间阶段合成的蛋白质控制，包括最初从L4启动子(L4P)表达的表观分子质量为22,000和33,000 Da的L4蛋白(L4-22K和-33K蛋白)。L4P被病毒蛋白和细胞P53结合激活，并最终被其自身的产物再次抑制。在这里，我们已经详细地检测了人腺病毒5型的L4P，并定义了它的转录起点，我们的数据表明它是由一个弱的TATA框定位的。转录起始点的一个假定的启动子元件不是对启动子活性起积极作用，而是作为细胞TFII-I对L4P实施负调控的目标。我们表明，这种TFII-I抑制被先前定义的L4P的病毒激活剂之一E4Orf3蛋白解除，它改变了细胞中的TFII-I池。我们还进一步探讨了其产物对L4P的负调控作用，表明L4-33K蛋白在这一过程中比L4-22K蛋白更重要。正是由于正负因素的共同作用，导致了L4P在腺病毒基因表达后期的瞬时激活。重要性腺病毒复制周期经历了基因表达的多个阶段，其中一个关键步骤是激活晚期基因表达，以产生可形成后代颗粒的蛋白质。通过与人5型腺病毒的合作，我们先前证明了从病毒基因组的L4区域表达的两种蛋白质在将感染转移到晚期方面起着至关重要的作用；这两种蛋白质是由专用启动子L4P产生的，如果没有它们，感染就不会成功地进行到后代。在这项新的工作中，我们描绘了L4P活性和调节的进一步方面。了解L4P是如何发挥作用的，以及它如何促进感染后期的激活，对于我们理解病毒的自然感染很重要，在这种感染中，晚期基因表达可能无法发生，从而使病毒得以持续。
The late phase of adenovirus gene expression is controlled by proteins made in the intermediate phase, including L4 proteins of 22,000- and 33,000-Da apparent molecular mass (L4-22K and -33K proteins) that are expressed initially from the L4 promoter (L4P). The L4P is activated by a combination of viral proteins and cellular p53 and is ultimately inhibited again by its own products. Here, we have examined the L4P of human adenovirus type 5 in detail and have defined its transcription start site, which our data suggest is positioned by a weak TATA box. Rather than contributing positively to promoter activity, a putative initiator element at the transcription start site acts as a target for negative regulation imposed on the L4P by cellular TFII-I. We show that this TFII-I inhibition is relieved by one of the previously defined viral activators of the L4P, the E4 Orf3 protein, which alters the pool of TFII-I in the cell. We also explore further the negative regulation of the L4P by its products and show that the L4-33K protein is more significant in this process than L4-22K. It is the combined actions of positive and negative factors that lead to the transient activation of the L4P at the onset of the late phase of adenovirus gene expression. IMPORTANCE The adenovirus replication cycle proceeds through multiple phases of gene expression in which a key step is the activation of late-phase gene expression to produce proteins from which progeny particles can be formed. Working with human adenovirus type 5, we showed previously that two proteins expressed from the L4 region of the viral genome perform essential roles in moving the infection on into the late phase; these two proteins are produced by the action of a dedicated promoter, the L4P, and without them the infection does not proceed successfully to progeny generation. In this new work, we delineate further aspects of L4P activity and regulation. Understanding how the L4P works, and how it contributes to activation of the late phase of infection, is important to our understanding of natural infections by the virus, in which late gene expression can fail to occur, allowing the virus to persist.