Effects of metacognitive reading strategy instruction on EFL high school students' reading comprehension, reading strategies awareness, and reading motivation.

摘要

A productive poxvirus infection is heavily dependent upon the synthesis of a vast array of host modulatory products that specifically target and manipulate both extracellular immune response pathways of the host as well as intracellular signal transduction pathways of the individually infected cells. The unique pathogenesis and host tropism of specific poxviruses can be attributed to the broad diversity of host modulatory proteins they express. Most poxviruses express multiple proteins containing ankyrin (ANK)-repeats accounting for a large superfamily of related but unique determinants of poxviral tropism. Recently, select members of this novel family of poxvirus proteins have drawn considerable attention for their potential roles in modulating intracellular signaling networks during viral infection. M-T5 is an ANK-repeat protein encoded by the rabbit-specific poxvirus, myxoma virus (MYXV) which functions to regulate tropism of MYXV for rabbit lymphocytes and some human cancer cells. At the molecular level, M-T5 binds and alters at least two distinct cellular proteins: Akt and cullin 1. Furthermore, the direct interaction between M-T5 and Akt was shown to upregulate the kinase activity of Akt and enhance viral replication in a spectrum human cancer cells. The aim of this study was to examine the molecular mechanism by which the M-T5 protein interacts with and manipulates host proteins to establish an intracellular environment leading to a productive viral replication.;To understand the significance of these viral-host protein interactions, the various binding domains of M-T5 were mapped. The N-terminal ANK-repeats I and II were identified as being important for interaction with Akt, whereas the C-terminal PRANC/F-box like domain was essential for binding to Skp1. We also report that M-T5 binds Akt and the host Skp-cullin-F-Box (SCF) complex (via Skp1) simultaneously in MYXV-infected cells. Furthermore, M-T5 specifically mediates the re-localization of Akt from the nucleus to the cytoplasm during infection with the wild-type MYXV, but not the M-T5 knockout version of the virus. When an array of Akt inhibitor compounds that selectively manipulate the Akt signaling network were screened, certain inhibitors significantly blocked MYXV replication in previously permissive human cancer cells. In contrast PP2A specific phosphatase inhibitors, such as okadaic acid, promoted an increased Akt kinase activation and rescued MYXV replication in human cancer cells that did not previously support viral replication. It was also demonstrated that hemi-phosphorylation of Akt at residue Thr308 dictates physical interaction between Akt and M-T5, which ultimately leads to productive MYXV replication in Type II cancer cells. Finally, we conclude that M-T5 is functionally interchangeable with the host PIKE-A protein, and that the activation of host Akt by either M-T5 or PIKE-A is critical for the permissiveness of human cancer cells by MYXV.;In summary, this study further examines the intricate relationship between M-T5 and components of the host cell signaling networks and how these elaborate interactions can profoundly impact poxvirus tropism. Currently, little is known regarding the factors that regulate poxvirus tropism and the mechanisms by which poxviral encoded ANK-repeat proteins micromanipulate the signaling pathways of the infected cell to establish an environment that favors virus replication. Understanding the function of this unique family of viral host range genes will prove to be incredibly useful in our efforts to decipher the mechanisms that regulate poxvirus tropism. More importantly, this knowledge will further develop poxviruses as potential oncolytic candidates, as selectively replicating vaccine platforms, and for other diverse biotherapeutic applications. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)