Doctor of Philosophy, Miami University, 2014, Microbiology

Cellular genomic integrity is constantly attacked by a variety of exogenous and endogenous agents. In response to damaged DNA, the cell activates a DNA damage response (DDR) pathway to maintain genomic integrity. Cells can also activate DDRs in response to infection with several types of viruses. The cellular DDR pathway involves sensing DNA damage by the Mre11, Rad50, Nbs1 (MRN) sensor complex, which activates downstream ataxia-telangiectasia mutated (ATM) and ATM-Rad3-related (ATR) kinases. These kinases phosphorylate downstream effector proteins implicated in cell cycle arrest, DNA repair, and, if the damage is irreparable, apoptosis. The induction of DDRs includes focal accumulation and phosphorylation of several DDR proteins. Adenovirus (Ad) mutants that lack early region 4 (E4) activate a cellular DDR. E4 proteins normally inactivate the MRN sensor complex and prevent downstream DDR signaling involved in DNA repair and cell cycle checkpoint arrest in wild-type Ad5 infections. The characteristics of Ad infection that activate the cellular DDR are not well understood. We have investigated the ability of replication defective and replication competent Ad mutants to activate cellular DDRs and G2/M cell cycle arrest. Ad infection induced early focal accumulation of DDR proteins such as Mre11, Mdc1, phosphorylated ATM (pATM), phosphorylated Chk2 (pChk2), and 53BPI, independent of the replication status of the mutants studied. However, Mre11 and pATM foci were transient in replication defective infections and were only maintained in infections with replication competent mutants. Viral DNA replication was correlated with amplification of pATM levels as well as its substrates, pChk2 and pNbs1. Furthermore, we found that G2/M cell cycle arrest was not activated by a replication defective mutant or a mutant expressing the E4orf3 encoded 11kDa protein. Our results suggest that the initial induction of DDR foci does not require viral DNA replication. In contrast, viral DNA (open full item for complete abstract)

Committee: Eileen Bridge (Committee Chair); Gary Janssen (Committee Member); Joseph Carlin (Committee Member); Xiao-Wen Cheng (Committee Member); David Pennock (Committee Member) Subjects: Microbiology

PhD, University of Cincinnati, 2008, Business: Business Administration

A “psychological contract” exists when an individual perceives that another party hasobligated itself to a reciprocal exchange relationship with him/herself. Most researchers exploring this concept tend to focus solely on the exchange relationship existing between the individual and a unitary “employer” (e.g., Coyle-Shapiro & Conway, 2005; King & Bu, 2005; Raja, Johns, & Ntalianis, 2004; Rousseau, 2000; Rousseau, 2004; Sels, Janssens, & Van den Brande, 2004). However, it is important to note that psychological contract theory is not limited in scope to this specific exchange relationship. Rather, the concept can also be applied to the individual…#8482;s relationships with “…a client, customer, supplier, or any other interdependent party” (Italics added: Rousseau, 1995: 34). Unfortunately, the implications of this theoretical flexibility are largely unexplored in academic research. The central premise of this dissertation is that individuals have simultaneous distinct but related psychological contracts with various individuals and groups operating within an organizational context, and the purpose is to examine the psychological contract concept from this multi-foci perspective. I accomplish this purpose through a three-stage survey-based research study. The sample population for the study was the entire incoming class of freshman at the business college of a large mid-western university. In Stage One, I investigated the nature of psychological contracts in my sample. This exploratory stage: 1) theoretically justified my research sample through an examination of archival data, 2) determined the foci of student psychological contracts through open-ended qualitative survey questions, and 3) determined the content of student psychological contracts through open-ended qualitative survey questions. In Stage Two, I used a quantitative survey methodology. Exploratory factor analyses were done to develop new measures of psychological contract content, and structural equat (open full item for complete abstract)

Committee: Suzanne Masterson PhD (Committee Chair); Elaine Hollensbe PhD (Committee Member); Karen Machleit PhD (Committee Member); David Lundgren PhD (Committee Member) Subjects: Management; Social Psychology

Doctor of Philosophy, Miami University, 2007, Microbiology

Eukaryotic cells possess mechanisms that monitor breaks in genomic DNA and repair them. The effectors of double strand break repair (DSBR) comprise a variety of proteins, including the Mre11/Rad50/Nbs1 (MRN) complex and the mediator of DNA damage checkpoint protein 1 (Mdc1). The Adenovirus (Ad) genome is linear, double stranded DNA that can be a substrate for “repair” by host DSBR proteins that link genomes end-to-end forming concatemers. The virus defends itself against this repair by producing regulatory proteins that interfere with DSBR. Early region 4 (E4) orf3-11kDa protein relocalizes the cellular MRN complex to nuclear track-like structures. The E4-orf6 34kDa/E1b-55kDa complex targets MRN for proteasome mediated degradation. Mutants that lack the E4-11kDa and 34kDa proteins activate the cellular damage response and are severely defective for DNA replication. We have investigated roles for the MRN complex and Mdc1 as sensors and effectors of damage signaling in an Ad-E4 mutant infection, particularly related to the onset of an efficient viral DNA replication. Briefly, we find that the MRN complex regulates the re-localization of Mdc1 early in the infection with an E4 mutant virus, consistent with its role as a sensor of DNA damage. Mdc1 is re-localized in response to viral infection and binds E4 mutant viral DNA, but does not appear to have a role in the regulation of viral DNA replication. The MRN complex, however, is relocalized to E4 mutant viral DNA replication centers in an Nbs1 dependent manner and binds viral DNA. The Nbs1 dependent binding of the complex to E4 mutant viral DNA inhibits the efficient onset of viral DNA replication consistent with the role of the MRN complex as an effector in the damage response and repair pathway. Investigating the ability of host DSBR proteins to interfere with E4 mutant DNA synthesis provides a model for understanding the mechanism by which these proteins sense and respond to the presence of aberrant or damaged DNA.

Committee: Eileen Bridge (Advisor) Subjects: