NOVEL CELL CYCLE REGULATION BY ADENOVIRUS E1B 55K

腺病毒E1 B 55-kDa（55 K）蛋白在病毒生长和病毒介导的细胞转化过程中发挥作用。 在病毒生长期间，55 K蛋白结合E4 orf 6蛋白并调节mRNA生物合成。在转化过程中，55 K蛋白结合肿瘤抑制因子p53并阻断p53应答基因的转录，包括促进细胞凋亡和诱导G1期生长停滞的基因。 然而，大多数感染55 K突变病毒的细胞不会发生凋亡，不会停滞在G1期，也不会无法复制突变病毒DNA。因此，55 K在病毒生长和转化中的功能之间的联系仍然不清楚。 这项工作将阐明这一联系的一部分，更大的目标是了解腺病毒的目标细胞生长控制病毒生长的机制。由于55 K突变病毒仅在S期早期感染而非G1期感染的HeLa细胞中生长，因此55 K蛋白克服了细胞周期对病毒生长的限制。 这一限制和克服这一限制的55 K功能将由三个具体目标决定。 首先，假设腺病毒必须篡夺mRNA的控制细胞周期无关的增长将进行评估，通过比较相关的G1限制性腺病毒突变体的增长和感染的细胞，是允许和限制病毒生长的mRNA运输的控制。 其次，允许和限制性细胞的异核体将被用来阐明这种限制的细胞基础，并确定限制性表型的优势。第三，将鉴定由55 K/E4 orf 6复合物靶向的用于细胞周期非依赖性病毒生长的细胞蛋白，并确定这些蛋白的细胞周期调节。这项研究将确定55 K蛋白如何破坏病毒生长的细胞周期控制。 这可能代表了55 K蛋白在裂解生长和病毒转化中的滚动之间的第一个联系。这些研究将增加我们对病毒发病机制和病毒肿瘤发生机制以及细胞生长控制的基本机制的理解。此外，本研究将鉴定限制在S期细胞中生长的腺病毒突变体。 此类可复制病毒可用作溶瘤剂以治疗快速生长的人肿瘤。

The adenovirus E1B 55-kDa (55K) protein functions during virus growth and virus-mediated cellular transformation. During virus growth, the 55K protein binds the E4orf6 protein and regulates mRNA biogenesis. During transformation, the 55K protein binds the tumor suppressor p53 and blocks transcription from p53-responsive genes including those that promote apoptosis and induce G1 growth arrest. However, most cells infected with the 55K-mutant virus do not undergo apoptosis, do not arrest in G1, and do not fail to replicate mutant viral DNA. Consequently, the link between 55K function in virus growth and transformation remains unclear. This work will elucidate this link as part of the larger goal of understanding the means by which adenovirus targets mechanisms of cellular growth control for virus growth. Because 55K-mutant viruses grow only in HeLa cells that were infected in early S phase but not in G1, the 55K protein overcomes a restriction imposed on virus growth by the cell cycle. This restriction and the 55K function that overcomes this restriction will be determined by three specific aims. First, the hypothesis that adenovirus must usurp the control of mRNA for cell cycle-independent growth will be evaluated by comparing the growth of related G1-restricted adenovirus mutants and the control of mRNA transport among infected cells that are permissive and restrictive for virus growth. Second, heterokaryons of permissive and restrictive cells will be used to elucidate the cellular basis for this restriction and determine the dominance of the restrictive phenotype. Third, cellular proteins targeted by 55K/E4orf6 complex for cell cycle-independent virus growth will be identified and the cell cycle- regulation of these proteins determined. This study will determine how the 55K protein subverts cell cycle controls for virus growth. This may represent the first link between the roll of the 55K protein in lytic growth and viral transformation. These studies will increase our understanding of the mechanisms of viral pathogenesis and viral oncogenesis as well as fundamental mechanisms of cellular growth control. Furthermore, this study will identify adenovirus mutants that are restricted for growth in S phase cells. Such replication competent viruses can be used as oncolytic agents to treat rapidly growing human tumors.