|
|
|
|
| Abstract |
|
|
|
|
Session 8
Symposium Host-Virus Interactions Session Time: Monday, 2 - 4 pm Room 6C |
Background: The viral infectivity factor (Vif) of human immunodeficiency virus type-1 (HIV-1) is a basic Mr-23,000 protein that occurs principally in the cytosol. Although vif is one of the most important accessory genes of HIV-1, it has a complex phenotype that has hindered its investigation. It is necessary for infectious HIV-1 production by T-lymphocytes and macrophages and some leukemic T-cell lines termed non-permissive (NP), but is irrelevant in other cells termed permissive (P). Methods: We have initiated a systematic effort to identify the cellular factor(s) that interact with Vif to control HIV-1 infectivity. Evidence that PxNP heterokaryons are NP suggested that NP cells contain a potent inhibitor of HIV-1 infectivity and that this cellular antiviral factor is neutralized by Vif. Furthermore, other studies have also implied that Vif function requires its association with an unknown cellular factor in NP cells. By using a human lymphocyte cDNA library in a yeast 2-hybrid screen with Vif as bait, we identified the nuclear body (NB) protein Sp140 as a potential binding partner of Vif. Sp140 has multiple isoforms and was previously shown to be lymphocyte- and macrophage-specific and to occur in some leukemic T-cell lines. Results: By Northern blot analyses, we found Sp140 in all NP cells but not in any leukemic T-cell lines that are P (n=12; p~0.001). Several mutations that inactivate Vif biological activity strongly inhibit its association with Sp140. HIV-1 infection stimulated partial dispersal of Sp140 from NBs into the cytosol, and Sp140 was then co-immunoprecipitated with Vif from cytosolic extracts. HIV-1 infections of P or NP cells also induced synthesis of an Sp140-related neo-antigen that formed clusters underlying plasma membranes. Expression of Sp140 in HeLa-CD4 cells induced Sumo-1 attachment onto at least 1 cellular protein, and this was prevented by Vif. Sp140 is related to the more widely expressed NB protein Sp100, which associates with PML and has been previously implicated in defenses against other viruses. Conclusions: Our results are consistent with the hypothesis that at least 1 isoform of Sp140 may be potent inhibitor of HIV-1 infectivity that is neutralized by Vif. A major implication of our studies is that the natural cellular targets of HIV-1, namely lymphocytes and macrophages, contain a potent innate antiviral pathway capable of inactivating HIV-1. |
|
©2002 9th Conference on Retroviruses and Opportunistic Infections |
