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James Chodosh, Jeong Yoon Lee, Ji Sun Lee, Emma Materne, Rahul Rajala, Ashrafali Ismail, Donald Seto, David Dyer, Jaya Rajaiya; Bacteria-driven evolution of human adenoviruses. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5619.
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© ARVO (1962-2015); The Authors (2016-present)
Human adenovirus species D (HAdV-D) is rapidly evolving, including those viruses that cause epidemic keratoconjunctivitis (EKC), an important eye infection. It has been previously established that HAdV-D persistently infect the human gastrointestinal tract, where bacterial and bacteriophage flora are abundant. We sought to determine whether bacterial/bacteriophage homologous recombination machinery can play a role in the ontogeny of new HAdV-D.
The viral genomes of 38 HAdV-D were analyzed in silico for the presence of crossover hotspot instigator (Chi) sequence motifs. Paired constructs containing the recombination hotspot for the HAdV-D penton base hypervariable loop 2 (RGD loop) were generated with the gene for green fluorescent protein in one construct and a CMV promoter in the other, such that fluorescence could occur only upon recombination. These constructs and HAdV-D co-infections were used to determine a potential role for bacterial Rec proteins in viral recombination. ssDNA secondary structures were predicted with mFold. ChIP analysis was performed to determine specificity of binding of bacterial enzymes to viral genomes. Confocal microscopy was applied to determine the potential co-localization of EdU-labeled viral DNA with Rec proteins.
Sequence motifs similar to bacterial Chi sequences, referred to here as ChiAD, were identified just 5’ to the coding region for penton base hypervariable loop 2. In constructs, ChiAD sequence and secondary structure both impacted recombination. Co-infection with two HAdV-Ds in the presence of E. coli proteins increased recombination between viruses, not seen with a RecA mutant strain, DH5α, or upon RecA depletion by immunomagnetic beads. By ChIP analysis, RecA bound specifically to ChiAD sequence relative to other regions of the adenovirus genome. Finally, in HAdV-D infected cells, Rec proteins entered cell nuclei and colocalized with viral DNA.
HAdV-D appropriation of bacterial recombination machinery facilitates viral evolution, a unique example of bacterial commensalism. Our findings may explain the recent emergence of new EKC viruses.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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