A novel fully-spliced accessory gene in equine lentivirus with distinct Rev-responsive element

Abstract

All lentiviruses encode an accessory protein Rev, whose main biological function is to mediate the nuclear export of unspliced and incompletely spliced viral transcripts by binding to a viral cis-acting element (termed the Rev-responsive element, RRE) that is located within env-encoding region. Equine infectious anemia virus (EIAV) is a member of the Lentivirus genus in the Retroviridae family, and is considered an important model for the study of lentivirus pathogenesis. Here, we identified a novel transcript from the EIAV genome that encodes a viral protein, named Mat, with unknown function. The transcript mat is fully spliced and comprises parts of the coding regions of MA and TM. Interestingly, the expression of Mat depends on Rev and the Crm1 pathway. Rev could specifically bind to Mat mRNA to promote its nuclear export. We further identified that the first exon of Mat mRNA, which is located within the Gag-encoding region, acts as an unreported RRE. Altogether, we identified a novel fully spliced transcript mat with an unusual RRE, which interacts with Rev for nuclear export through the Crm1 pathway. Our findings may help to expend the understanding of gene transcription and expression of lentivirus.