Regulation of Rev expression by the equine infectious anaemia virus tat-rev mRNA Kozak sequence and its potential influence on viral replication

Rev, an important accessory protein of equine infectious anaemia virus (EIAV), induces the nuclear export of incompletely spliced viral mRNAs. Rev is translated from the tat-rev mRNA through leaky scanning of the tat CUG. In this study, the function of the Kozak sequence at the beginning of the rev ORF was investigated. Deletion or attenuation of the Kozak sequence resulted in expression of an N-terminal 11 aa-truncated Rev in addition to WT Rev. Truncated Rev displayed weaker promotion of Gag expression and processing than WT Rev. Furthermore, EIAV rescued from an infectious molecular clone (pEIAVUK3) with Kozak attenuation exhibited decreased viral replication in host cells in vitro. These results provide a new understanding of the relationship between EIAV Rev expression and viral replication.