Eukaryotic translation elongation factor 1 alpha (eEF1A) inhibits Siniperca chuatsi rhabdovirus (SCRV) infection through two distinct mechanisms

Abstract

ABSTRACT Rhabdoviruses are single-stranded, negative-sense RNA viruses with broad host range, several of which are important pathogens. Compared with the rhabdoviruses infecting mammals, host factors involved in aquatic rhabdovirus infection have remained largely unknown. In the present study, we report the roles of host eukaryotic translation elongation factor 1 alpha (eEF1A) on the infection of Siniperca chuatsi rhabdovirus (SCRV, genus Siniperhavirus ), which is an important pathogen of mandarin fish. eEF1A was identified from SCRV nucleoprotein (N)-based affinity purified proteins. Further protein interaction and mutation assays proved that eEF1A interacted not only with the N protein but also the virus matrix protein (M), which relied on the N-terminal of eEF1A. SCRV infection and overexpression of N or M all stimulated the promoter activity of the eEF1A gene and, thus, upregulated its expression, whereas the upregulated eEF1A inhibited the transcription of SCRV genome. Mechanistically, eEF1A impaired the interactions between N and phosphoprotein (P), or N and N, which are important for the efficient transcription and replication of rhabdovirus. Meanwhile, eEF1A promoted the ubiquitin-proteasome degradation of the M protein, which relied on lysine 48 (K48) of ubiquitin. In addition, we showed that the ubiquitination degradation of M protein relied on C-terminal domain of eEF1A, but inhibition of the N-P or N-N interactions needs its entire length. Collectively, these results revealed two different mechanisms used by eEF1A to resist a fish rhabdovirus, which provided novel insights into the role of eEF1A in rhabdovirus infection and new information for antiviral research. IMPORTANCE Although a virus can regulate many cellular responses to facilitate its replication by interacting with host proteins, the host can also restrict virus infection through these interactions. In the present study, we showed that the host eukaryotic translation elongation factor 1 alpha (eEF1A), an essential protein in the translation machinery, interacted with two proteins of a fish rhabdovirus, Siniperca chuatsi rhabdovirus (SCRV), and inhibited virus infection via two different mechanisms: (i) inhibiting the formation of crucial viral protein complexes required for virus transcription and replication and (ii) promoting the ubiquitin-proteasome degradation of viral protein. We also revealed the functional regions of eEF1A that are involved in the two processes. Such a host protein inhibiting a rhabdovirus infection in two ways is rarely reported. These findings provided new information for the interactions between host and fish rhabdovirus.