Cleavage of chicken vimentin by the reticuloendotheliosis virus protease

Abstract

The protease (PR) encoded by reticuloendotheliosis virus (REV) is deeply involved in the lifecycle and infection process of a virus in that it cleaves the viral polyproteins into their mature structural proteins and replication enzymes. Besides this essential role in the lifecycle of a virus, the enzymatic activity of the REV PR targeting chicken vimentin remains unknown. In this study, the recombinant chicken vimentin, fused with a GST-tag, was expressed in the Escherichia coli system as a soluble form. The soluble vimentin was purified using Glutathione Sepharose 4B. Then, the in vitro cleavage of chicken vimentin by the PR of REV was analyzed. The results showed that chicken vimentin was cleaved by the REV PR. Furthermore, Nano LC-MS/MS analysis showed that the REV PR cleaved chicken vimentin between leucine-239 and glutamine-240, alanine-261 and alanine-262, and histidine-431 and serine-432, respectively. Moreover, the cleavage sites identified in this study were different from other known naturally occurring cleavage sites of other retroviruses. For the first time, we showed that the REV PR cleaved the chicken vimentin at specific sites in chicken vimentin. These results support the possibility that chicken vimentin may serve as a substrate within REV-infected cells, facilitating our understanding of avian retroviruses.