POSTER ABSTRACT Undergraduate Presenter: Caleb Swaim (‘13) Endogenous Retrovirus-­‐Fc is a Tool for Exploring Host Virus Interaction 1
Authors: Caleb D. Swaim , William E. Diehl1, Nirali M.Patel1, Welkin E. Johnson1 1
Department of Biology, Boston College, Chestnut Hill, MA, USA Up to 10 percent of vertebrate genomes consist of endogenous retroviral (ERV) sequences that exist as records of previous retroviral outbreaks. This molecular “fossil record” can be exploited to assess the evolutionary past of both the virus and the host. The vast majority of ERVs have accumulated inactivating mutations, including point mutations, insertions, or deletions. Previous reports have shown that a gamma-­‐like family of endogenous retroviruses, ERV-­‐Fc, has independently maintained env open reading frames in humans, baboons, and marmosets†. As the probability of endogenization and subsequent maintenance of intact ORFs is incredibly low, studying this family of ERVs could yield valuable insight into how these viruses and hosts co-­‐
evolved. Toward this end, we attempted to reconstruct a reverse genetics system through synthetic gene synthesis and expression of a consensus Old World primate ERV-­‐Fc. We compiled all complete, or nearly complete, ERV-­‐Fc sequences from the rhesus macaque genome as well as additional sequences from baboon and African green monkey. From these, a consensus sequence, weighted toward loci that contained complete gag, pol, and env sequences, was generated and synthesized. However, following transfection into 293T cells no ERV-­‐Fc protein was produced. In an attempt to obtain protein production, a version of ERV-­‐Fc gag was synthesized in which the codons were substituted for those most frequently found in highly expressed genes, while any potential splice sites and RNA secondary structures were removed. These modifications resulted in robust Gag production, as detected by western blot. In order to assess which regions inhibit protein production in the native gag sequence a series of chimeras between the “codon optimized” and the native sequence were generated. These chimeras demonstrate that such determinants are in the 5’ end of matrix as well as in capsid.