Human immunodeficiency virus‐1 Nef protein interacts with Tat and enhances HIV‐1 gene expression

Abstract

The human immunode¢ciency virus (HIV-1) Nef protein is now regarded as a regulatory protein responsible not only for establishment of infection and increased pathogenesis but also for enhancement of viral replication. However, the mechanism of Nef-induced activation of viral replication remains to be clearly understood. Using transient transfection assay, co-immunoprecipitation and pull-down analysis, we demonstrate in this report that the HIV-1 Nef protein physically interacts with Tat, the principal transactivating protein of HIV-1. Our observations with single cycle replication experiments further indicate that this interaction results not only in enhancement of Tat-induced HIV-1 long terminal repeat-mediated gene expression but also in virus production. ß

Displacement of SATB1-Bound Histone Deacetylase 1 Corepressor by the Human Immunodeficiency Virus Type 1 Transactivator Induces Expression of Interleukin-2 and Its Receptor in T Cells

“…We used chromatin from CEM-GFP, a stable CD4 ϩ T-cell line containing a plasmid encoding the green fluorescent VOL. 25,2005 HIV-1 Tat DISRUPTS SATB1-HDAC1 COMPLEX 1621 protein driven by the HIV-1 LTR promoter (17). This cell line has been used widely as a reporter cell line to monitor HIV infection.…”

“…The IL-2 promoter (45)-luciferase reporter construct was obtained from K. McGuire. For cotransfections we used p3XFLAG-CMV10-SATB1, pCDNA3.1-Tat (25), and pBJ5-HDAC1 at 1 to 2 g/well either singly or in different combinations along with the reporter constructs at 1 g/well. HEK 293 cells were seeded at 0.2 ϫ 10 6 cells per well and transfected using Lipofectamine 2000 reagent (Invitrogen).…”

HIV-1 Tat Suppresses gp120-Specific T Cell Response in IL-10-Dependent Manner

“…The subtype B Tat sequence was subcloned in the multiple cloning site B of pIRES taken from the pCDNA-Tat vector previously reported from this laboratory (24). The subtype C gp120 sequence was also cloned in pCDNA3.1 (Invitrogen Life Technologies).…”

Cyclin K Inhibits HIV-1 Gene Expression and Replication by Interfering with Cyclin-dependent Kinase 9 (CDK9)-Cyclin T1 Interaction in Nef-dependent Manner

“…Although a number of reports show that Nef increases viral replication by activating T-cells, the molecular basis of Nef-induced viral gene expression and replication remains to be clearly elucidated. Nef was also shown to physically interact with Tat and augment viral gene expression (16), although availability of Tat is critical for the elongation step of long terminal repeat (LTR) 2 -driven transcription by RNA polymerase II. Several cellular factors have been identified for their roles in this process, including positive transcription elongation factor b (P-TEFb) complex.…”

“…The complex between CycK and CDK9 was also shown to function as a CTD kinase in vitro (17). Although Nef was earlier reported as a negative factor for viral replication (32), recent evidence has convincingly demonstrated Nef as an enhancer of viral replication (16,22,(33)(34)(35)(36). Nef performs most of its functions by interacting with cellular proteins.…”