Date of Award

Spring 4-18-2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

First Advisor

Teryl Frey

Abstract

The rubella virus (RUB) capsid protein (C) is a multifunctional phosphoprotein with roles beyond encapsidation. It is able to rescue a large lethal deletion of the Q domain in the P150 replicase gene at a step in replication before detectable viral RNA synthesis, indicating a common function shared by RUB C and the Q domain. The goal of this dissertation was to use constructs containing the N-terminal 88 amino acids of RUB C, the region previously defined as the minimal region required for the rescue of Q domain mutants, to elucidate the function of RUB C in Q domain rescue and viral RNA synthesis. In the first specific aim, the rescue function of 1-88 RUB C and the importance of an arginine-rich cluster, R2, within 1-88 RUB C for rescue were confirmed. Rescue was not correlated with intracellular localization or phosphorylation status of RUB C. In the second specific aim, the involvement of RUB C in early events post-transfection with RUB RNA was analyzed. RUB C specifically protected RUB transcripts early post-transfection and protection required R2. However, it was concluded the protection observed was due to the encapsidation function of RUB C and not related to Q domain rescue. No differences in the translation of the RUB nonstructural proteins in the presence or absence of RUB C were observed. Interactions of RUB C with host cell proteins were analyzed. Although the interaction of RUB C with cellular p32 required the R2 cluster, both wild type (does not require RUB C for replication) and RQQ (requires RUB C for replication) Q domain bound p32, indicating interaction with this binding partner is not the basis of rescue. Using a human protein array phosphatidylinositol transfer protein alpha isoform (PITPα) was found to interact with RUB C but not its R2 mutant. However, co-immunoprecipitation experiments revealed that this protein binds both forms of RUB C. Although the mechanism behind the rescue of the RUB P150 Q domain by RUB C remains unknown, we propose a model that RUB C plays a role in generation of the virus replication complex in infected cells.

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