Specific cleavage sites of Nef proteins from human immunodeficiency virus types 1 and 2 for the viral proteases

Abstract

Human immunodeficiency virus type 2 (HIV-2) Nef is proteolytically cleaved by the HIV-2-encoded protease. The proteolysis is not influenced by the absence or presence of the N-terminal myristoylation. The main cleavage site is located between residues 39 and 40, suggesting a protease recognition sequence, GGEY-SQFQ. As observed previously for Nef protein from HIV-1, a large, stable core domain with an apparent molecular mass of 30 kDa is produced by the proteolytic activity. Cleavage of Nef from HIV-1 in two domains by its own protease or the protease from HIV-2 is also independent of Nef myristoylation. However, processing of HIV-1 Nef by the HIV-2 protease is less selective than that by the HIV-1 protease: the obtained core fragment is heterogeneous at its N terminus and has an additional cleavage site between amino acids 99 and 100. Preliminary experiments suggest that the full-length Nef of HIV-2 and the core domain are part of the HIV-2 particles, analogous to the situation reported recently for HIV-1.

Association of Human Immunodeficiency Virus Nef Protein with Actin is Myristoylation Dependent and Influences its Subcellular Localization

“…However, there is accumulating evidence that cleavage of Nef by the viral protease within the particle is important for the enhancement of viral infectivity through Nef [60, 611. Although we demonstrated cleavage of HIV-2 Nef by HIV-2 protease in vitro [7], we failed to detect any specifically cleaved Nef associated with HIV-2 virions [20]. Thus, the impaired interaction between actin and Nef of HIV-2 might result in a less efficient processing of Nef by the viral protease, thereby possibly contributing to the reduced infectivity of HIV-2 compared with HIV-1.…”

The crystal structure of HIV-1 Nef protein bound to the Fyn kinase SH3 domain suggests a role for this complex in altered T cell receptor signaling

“…Nef is one of the first HIV proteins to be produced at high levels in infected cells and the most immunogenic of the regulatory proteins [2,3]. Several recent reports provide evidence that Nef is a virion-associated protein, specifically cleaved in the viral particle by the viral protease to form a stable core domain [12][13][14][15].…”

Characterization and molecular basis of the oligomeric structure of HIV‐1 Nef protein

“…The N-terminus of all Nef proteins is myristoylated and mediates membrane association. The core domain of Nef folds into a globular a-b protein, whereas the N-terminal and central loop region, i.e., 50% of the polypeptide chain, seem to be unstructured in an aqueous solvent~Grzesiek et al, 1996a;Lee et al, 1996;Arold et al, 1997;Barnham et al, 1997;Geyer et al, 1999!. Nef proteins are found incorporated in the HIV-1 viral particles and are cleaved by the viral protease~Freund et al, 1994aprotease~Freund et al, , 1994bGaedigk-Nitschko et al, 1995;Pandori et al, 1996;Schorr et al, 1996;Welker et al, 1996;Miller et al, 1997;Chen et al, 1998!. Incorporation and proteolytic cleavage in virions have equally been reported for HIV-2 Nef~Schorr et al, 1996!. The functional significance of the cleavage, which liberates the C-terminal core domain from its membrane associated N-terminus, remains unknown.…”