Abstract
Molecular basis of HIV-1 life cycle regulation has thus far focused on viral gene stage-specificity, despite the quintessence of post-function protein elimination processes in the virus life cycle and consequent pathogenesis. Our studies demonstrated that a key pathogenic HIV-1 viral protein, Nef, interacted with ubiquitin (Ub)-protein ligase E3A (UBE3A/E6AP), suggesting that interaction between Nef and UBE3A is integral to regulation of viral and cellular protein decay and thereby the competing HIV-1 and host cell survivals. In fact, Nef and UBE3A degraded reciprocally, and UBE3A-mediated degradation of Nef was significantly more potent than Nef-triggered degradation of UBE3A. Further, UBE3A degraded not only Nef but also HIV-1 structural proteins, Gag, thus significantly inhibiting HIV-1 replication in Jurkat T cells only in the presence of Nef, indicating that interaction between Nef and UBE3Awas pivotal for UBE3A-mediated degradation of the viral proteins. Mechanistic study showed that Nef and UBE3A were specific and antagonistic to each other in regulating proteasome activity and ubiquitination of cellular proteins in general, wherein specific domains of Nef overlapping with the long terminal repeat (LTR) were essential for the observed actions. Further, Nef itself reduced the level of intracellular Gag by degrading a cardinal transcription regulator, Tat, demonstrating a broad role for Nef in the regulation of the HIV-1 life cycle. Taken together, these data demonstrated that the Nef and UBE3A complex plays a crucial role in coordinating viral protein degradation and hence HIV-1 replication, providing insights as to the nature of pathobiologic and defense strategies of HIV-1 and HIV-infected host cells.
Highlights
To date, smooth transitioning from the early to late stage of HIV-1 life cycle has been mainly explained by a stage-specific expression of viral genes in the infected cells
Tat, rev, and nef genes are expressed at the early stage of HIV-1 infection, and the expressed Rev pumps out the structural genes harboring Rev-responsive element (RRE), such as gag, pol, and env, into the cytoplasm to produce the structural proteins at the late stage of virus life cycle in the infected cells [1,2,3,4,5]
Co-transfection with the UBE3A expresser along ith either the HIV-1- or SIVpbj1.9-nef expresser resulted in strong chloramphenicol acetyltransferase (CAT) enzymatic activity, while little activity was detected in cells transfected with either nef - or UBE3A-expresser (Figure 1B)
Summary
Smooth transitioning from the early to late stage of HIV-1 life cycle has been mainly explained by a stage-specific expression of viral genes in the infected cells. Tat, rev, and nef genes are expressed at the early stage of HIV-1 infection, and the expressed Rev pumps out the structural genes harboring Rev-responsive element (RRE), such as gag, pol, and env, into the cytoplasm to produce the structural proteins at the late stage of virus life cycle in the infected cells [1,2,3,4,5]. Little is known about how these individual events taking place at different stages of the virus life cycle are orchestrated and what viral and/or cellular elements are responsible for such regulation of intracellular viral and cellular protein degradation
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
