Cooperative interaction between HIV-1 regulatory proteins Tat and Vpr modulates transcription of the viral genome.
The virion-associated protein of human immunodeficiency virus, type 1 (HIV-1), Vpr, is a small protein with 96 amino acid residues that has the ability to modulate transcription of HIV-1 long terminal repeat (LTR) promoter activity and affects several cellular functions. In this study we have employed molecular approaches to further investigate the mechanism by which Vpr exerts its regulatory effect upon the LTR. We show that by structural and functional interaction with Tat, a potent viral regulatory protein, Vpr synergistically enhances the transcriptional activity of the HIV-1 LTR. Because Tat utilizes cyclin T1 and its partner, CDK9 to elevate the level of transcription from the LTR, we examined the cooperativity between Vpr, Tat, and cyclin T1/CDK9 on viral gene transcription. Results from co-transfection studies indicated superactivation of LTR by Tat and cyclin T1/CDK9 in the presence of wild type Vpr. This activation was not observed with the R73S mutant of Vpr, which contains arginine to serine transition at residue 73. Interestingly, expression of R73S mutant in cells exerts a negative effect on the observed superactivation of the LTR by Tat, cyclin T1/CDK9, and wild type Vpr. Results from protein-protein interaction studies indicated that Vpr is associated with both Tat and cyclin T1 in cells expressing these proteins. Use of deletion mutant proteins in binding studies revealed that the binding sites for Tat and Vpr within cyclin T1 are distinct and that association of these two viral proteins with cyclin T1 is independent from each other. These observations suggest a working model on the cooperative interaction of Vpr with viral and cellular proteins and its involvement in control of viral gene transcription and replication. Moreover identification of R73S mutant of Vpr provides a new therapeutic avenue for controlling HIV-1 gene transcription and replication in the infected cells.
Sawaya
B E
BE
Center for Neurovirology and Cancer Biology, College of Science and Technology, Temple University, Philadelphia, Pennsylvania 19122, USA.
Khalili
K
K
Gordon
J
J
Taube
R
R
Amini
S
S
D001120:Arginine / Q000737:chemistry; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D056906:Cyclin T; D042863:Cyclin-Dependent Kinase 9; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D017353:Gene Deletion; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism*; D016336:Gene Products, vpr / Q000235:genetics / Q000378:metabolism*; D005982:Glutathione Transferase; D015497:HIV-1 / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D016296:Mutagenesis; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D020079:Terminal Repeat Sequences / Q000235:genetics; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D054322:tat Gene Products, Human Immunodeficiency Virus; D054325:vpr Gene Products, Human Immunodeficiency Virus
C503684:CCNT1 protein, human; D056906:Cyclin T; D016213:Cyclins; D018076:DNA, Complementary; D015696:Gene Products, tat; D016336:Gene Products, vpr; D011993:Recombinant Fusion Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D054325:vpr Gene Products, Human Immunodeficiency Virus; D012694:Serine; D001120:Arginine; D005982:Glutathione Transferase; C467969:CDK9 protein, human; D042863:Cyclin-Dependent Kinase 9; D018844:Cyclin-Dependent Kinases