Doxorubicin inhibits Tat-dependent transactivation of HIV type 1 LTR.
Tat, the human immunodeficiency virus (HIV)-encoded transcription factor, is vital for HIV replication and transcription. Any drug that inhibits Tat's activity is a valuable candidate for chemotherapeutic applications. We show here that doxorubicin (Dox), a well-known anticancer drug and its derivative, daunomycin, inhibit the ability of Tat to activate the HIV-1 LTR. We contransfected HeLa cells with pSV40TAT and a chloramphenicol acetyltransferase gene driven by an HIV LTR promoter. CAT transcription was vigorously stimulated many fold by Tat production but the effect of Tat was inhibited by Dox in a dose-dependent manner. The transcriptional activation domain of Tat, located in its 67 amino terminal residues, remains Dox sensitive. A TAR-deleted reporter gene with a Gal binding domain is transactivated by a Gal-Tat fusion protein. This transcription complex retains a high level of activity in the presence of Dox, suggesting that Dox primarily affects RNA-Tat, rather than DNA-Tat, mediated transactivation. RNA gel mobility analysis reveals that Dox does not affect the binding of Tat to TAR-RNA in vitro but does increase the binding activity of cellular nuclear proteins with TAR-RNA. Induction or activation of such TAR-binding proteins in cells that might interfere with the activity of Tat could explain the observed inhibitory effects of Dox on Tat-activated transcription. These results suggest that Dox may have chemotherapeutic effects on HIV expression mediated through TAR RNA.
Jeyaseelan
R
R
Department of Biochemistry and Molecular Biology, University of Southern California School of Medicine, Los Angeles 90033, USA.
Kurabayashi
M
M
Kedes
L
L
D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D000998:Antiviral Agents / Q000494:pharmacology*; D004317:Doxorubicin / Q000494:pharmacology*; D015696:Gene Products, tat / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016325:HIV Long Terminal Repeat / Q000187:drug effects* / Q000235:genetics; D015497:HIV-1 / Q000187:drug effects*; D006367:HeLa Cells; D006801:Humans; D011485:Protein Binding / Q000187:drug effects; D012367:RNA, Viral / Q000187:drug effects / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects*; D015854:Up-Regulation; D054322:tat Gene Products, Human Immunodeficiency Virus
D000903:Antibiotics, Antineoplastic; D000998:Antiviral Agents; D015696:Gene Products, tat; D012367:RNA, Viral; D054322:tat Gene Products, Human Immunodeficiency Virus; D004317:Doxorubicin