The viral transactivator Rev is essential for HIV replication, since it allows the nuclear export of unspliced and partially spliced viral mRNAs that encode the structural proteins. Rev is an RNA binding protein that interacts with a highly structured RNA element, the RRE, found within the envelope sequences. This viral protein also interacts with cellular proteins, termed nucleoporins, and acts as an adaptor between the viral mRNAs and the cellular nuclear export machinery. Both interactions are specific, and required for Rev function. Because of its crucial role in the HIV replication cycle, and its novel mechanism of action, Rev represents an ideal target for therapeutic intervention. This review describes the efforts towards Rev inhibition. Gene therapy approaches, including the expression of trans-dominant mutants and RNA decoys, as well as antisense therapies and small molecule inhibitors of Rev-RRE binding or Rev interaction with the cellular machinery will be discussed.
INTRODUCTIONHIV-1, the etiologic agent of Acquired Immunodeficiency Syndrome (AIDS), displays a complex regulation of __________________________________________ Received 6/2/97 Accepted 6/4/97 1 To whom correspondence should be addressed at: Oncogene Science, Inc., 106 Charles Lindbergh Blvd., Uniondale, NY 11553 Tel: 516-222-0023 Fax: 516-222-0114 E-mail: aheguy@oncogene.com viral gene expression during its life cycle. Unlike many "simple" retroviruses (i.e. avian and murine leukemia viruses), which express only three viral genes, the genome of HIV-1 encodes nine genes whose expression patterns are tightly regulated during the HIV-1 replication cycle (Figure 1, for reviews see 1, 2, 3). In the infected host cell, HIV expresses over 20 distinct mRNA species (reviewed in 4). The early stage of regulation of the HIV-1 life cycle is marked by the appearance of the viral regulatory molecules Tat, Rev, and Nef, encoded by the fully spliced 2 kb class of viral mRNAs. The late viral life cycle gene expression is characterized by the cytoplasmic appearance of the 4 kb class of single spliced and 9.2 kb unspliced mRNAs, that encode the proteins required for the assembly of infectious virions. The viral transactivator Rev allows this transition into the late cycle (5, 6), and is therefore essential for viral replication. In effect, proviral mutants that do not express Rev fail to produce structural proteins and therefore cannot form new infectious viral particles (5, 7).Because of its essential role in HIV replication, Rev constitutes an excellent target for therapeutic intervention. Its mode of action and specific interactions with its target RNA and cellular proteins have been extensively studied and elegantly elucidated, and this body of knowledge adds to the attractiveness of Rev as a target. The purpose of this article is to briefly review the latest developments on Rev, and how this knowledge can be used for development of anti-viral strategies, as well as to