A novel motif in HIV-1 Nef that regulates MIP-1β chemokine release in macrophages

All primate lentiviruses encode Nef, an accessory protein that is important for viral pathogenicity in vivo. Lentiviral Nef proteins regulate the release of chemokines (MIP-1 α/β) from infected macrophages, thereby enhancing virus dissemination (S. Swingler, A. Mann, J. Jacque, B. Brichacek, V. G. Sasseville, K. Williams, A. A. Lackner, E. N. Janoff, R. Wang, D. Fisher, and M. Stevenson, Nat. Med. 5:997-1003, 1999). In the current study, we have identified a novel domain within Nef (K⁹²EK) that is required for Nef-dependent MIP-1β production by infected macrophages. Mutations in this domain abrogated MIP-1β induction but did not affect other Nef-ascribed activities, such as CD4 or major histocompatibility complex (MHC) class I downregulation. This further underscores Nef as a modular protein with genetically separable activities that may contribute to its role in viral replication and pathogenicity.