Second exon of Tat of HIV-2 is required for optimal trans-activation of HIV-1 and HIV-2 LTRs.
To determine conditions for optimal trans-activation by Tat of HIV-2, genomic DNAs and cDNAs encoding Tat of HIV-2 were tested on their homologous (HIV-2) and heterologous (HIV-1) long terminal repeats (LTRs). It has been previously reported that Tat of HIV-2 could efficiently trans-activate only its own LTR but not that of HIV-1. The inefficient trans-activation of HIV-1 is due, in part, to an acidic residue in the basic, RNA-binding domain of Tat of HIV-2. Here we demonstrate that inefficient trans-activation of HIV-1 LTR is observed only with plasmids that express exon 1 and genomic forms of tat of HIV-2. Expression of both exons of Tat of HIV-2 from cDNA results in trans-activation of HIV-1 that is equivalent to the effect of Tat of HIV-1. In addition, the cDNA form of tat of HIV-2 trans-activates the HIV-2 LTR more efficiently than exon 1 and genomic forms of tat of HIV-2. We conclude that exon 2 of Tat of HIV-2 is important for optimal interactions with the trans-acting responsive regions (TARs) of HIV-1 and HIV-2 and that differential expression of short and full-length Tats of HIV-2 during the viral life cycle might affect viral latency, levels of viral replication, and cellular cytopathology.
Tong-Starksen
S E
SE
Department of Medicine, Veterans Administration Medical Center, San Francisco, California 94121.
Baur
A
A
Lu
X B
XB
Peck
E
E
Peterlin
B M
BM
D000595:Amino Acid Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D005091:Exons; D015696:Gene Products, tat / Q000235:genetics* / Q000378:metabolism; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics*; D015498:HIV-2 / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D015533:Transcriptional Activation; D054322:tat Gene Products, Human Immunodeficiency Virus
D015696:Gene Products, tat; D054322:tat Gene Products, Human Immunodeficiency Virus