scholarly journals Role of Glucocorticoid Receptor Binding Sites in the Human Immunodeficiency Virus Type 1 Long Terminal Repeat in Steroid-Mediated Suppression of HIV Gene Expression

Virology ◽  
1995 ◽  
Vol 214 (2) ◽  
pp. 512-521 ◽  
Author(s):  
DEBASHIS MITRA ◽  
SANTOSH K. SIKDER ◽  
JEFFREY LAURENCE
Keyword(s):  
Gene Expression ◽  
Human Immunodeficiency Virus ◽  
Glucocorticoid Receptor ◽  
Long Terminal Repeat ◽  
Human Immunodeficiency Virus Type ◽  
Receptor Binding ◽  
Binding Sites ◽  
Immunodeficiency Virus

The NF-kappa B and Sp1 motifs of the human immunodeficiency virus type 1 long terminal repeat function as novel thyroid hormone response elements

1993 ◽  
Vol 13 (8) ◽  
pp. 5057-5069
Author(s):  
V Desai-Yajnik ◽  
H H Samuels
Keyword(s):  
Human Immunodeficiency Virus ◽  
Thyroid Hormone ◽  
Long Terminal Repeat ◽  
Human Immunodeficiency Virus Type ◽  
Binding Sites ◽  
Nf Kappa B ◽  
Response Elements ◽  
Immunodeficiency Virus ◽  
Hiv 1

We report that thyroid hormone (T3) receptor (T3R) can activate the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR). Purified chick T3R-alpha 1 (cT3R-alpha 1) binds as monomers and homodimers to a region in the LTR (nucleotides -104 to -75 [-104/-75]) which contains two tandem NF-kappa B binding sites and to a region (-80/-45) which contains three Sp1 binding sites. In contrast, human retinoic acid receptor alpha (RAR-alpha) and mouse retinoid X receptor beta (RXR-beta) do not bind to these elements. However, RXR-beta binds to these elements as heterodimers with cT3R-alpha 1 and to a lesser extent with RAR-alpha. Gel mobility shift assays also revealed that purified NF-kappa B p50/65 or p50/50 can bind to one but not both NF-kappa B sites simultaneously. Although the binding sites for p50/65, p50/50, and T3R, or Sp1 and T3R, overlap, their binding is mutually exclusive, and with the inclusion of RXR-beta, the major complex is the RXR-beta-cT3R-alpha 1 heterodimer. The NF-kappa B region of the LTR and the NF-kappa B elements from the kappa light chain enhancer both function as T3 response elements (TREs) when linked to a heterologous promoter. The TREs in the HIV-1 NF-kappa B sites appear to be organized as a direct repeat with an 8- or 10-bp gap between the half-sites. Mutations within the NF-kappa B motifs which eliminate binding of cT3R-alpha 1 also abolish stimulation by T3, indicating that cT3R-alpha 1 binding to the Sp1 region does not independently mediate activation by T3. The Sp1 region, however, is converted to a functionally strong TRE by the viral tat factor. These studies indicate that the HIV-1 LTR contains both tat-dependent and tat-independent TREs and reveal the potential for T3R to modulate other genes containing NF-kappa B- and Sp1-like elements. Furthermore, they indicate the importance of other transcription factors in determining whether certain T3R DNA binding sequences can function as an active TRE.

scholarly journals Evolution of the Human Immunodeficiency Virus Type 1 Long Terminal Repeat Promoter by Conversion of an NF-κB Enhancer Element into a GABP Binding Site

1999 ◽  
Vol 73 (2) ◽  
pp. 1331-1340 ◽  
Author(s):  
Koen Verhoef ◽  
Rogier W. Sanders ◽  
Veronique Fontaine ◽  
Shigetaka Kitajima ◽  
Ben Berkhout
Keyword(s):  
Human Immunodeficiency Virus ◽  
Transcription Factor ◽  
Long Terminal Repeat ◽  
Binding Site ◽  
Human Immunodeficiency Virus Type ◽  
Binding Sites ◽  
Immunodeficiency Virus ◽  
Ltr Promoter ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) transcription is regulated by the viral Tat protein and cellular factors, of which the concentration and activity may depend on the cell type. Viral long terminal repeat (LTR) promoter sequences are therefore optimized to suit the specific nuclear environment of the target host cell. In long-term cultures of a Tat-defective, poorly replicating HIV-1 mutant, we selected for a faster-replicating virus with a 1-nucleotide deletion in the upstream copy of two highly conserved NF-κB binding sites. The variant enhancer sequence demonstrated a severe loss of NF-κB binding in protein binding assays. Interestingly, we observed a new binding activity that is specific for the variant NF-κB sequence and is present in the nuclear extract of unstimulated cells that lack NF-κB. These results suggest that inactivation of the NF-κB site coincides with binding of another transcription factor. Fine mapping of the sequence requirements for binding of this factor revealed a core sequence similar to that of Ets binding sites, and supershift assays with antibodies demonstrated the involvement of the GABP transcription factor. Transient transfection experiments with LTR-chloramphenicol acetyltransferase constructs indicated that the variant LTR promoter is specifically inhibited by GABP in the absence of Tat, but this promoter was dramatically more responsive to Tat than the wild-type LTR. Introduction of this GABP site into the LAI virus yielded a specific gain of fitness in SupT1 cells, which contain little NF-κB protein. These results suggest that GABP potentiates Tat-mediated activation of LTR transcription and viral replication in some cell types. Conversion of an NF-κB into a GABP binding site is likely to have occurred also during the worldwide spread of HIV-1, as we noticed the same LTR modification in subtype E isolates from Thailand. This typical LTR promoter configuration may provide these viruses with unique biological properties.

scholarly journals The NF-kappa B and Sp1 motifs of the human immunodeficiency virus type 1 long terminal repeat function as novel thyroid hormone response elements.

1993 ◽  
Vol 13 (8) ◽  
pp. 5057-5069 ◽  
Author(s):  
V Desai-Yajnik ◽  
H H Samuels
Keyword(s):  
Human Immunodeficiency Virus ◽  
Thyroid Hormone ◽  
Long Terminal Repeat ◽  
Human Immunodeficiency Virus Type ◽  
Binding Sites ◽  
Nf Kappa B ◽  
Response Elements ◽  
Immunodeficiency Virus ◽  
Hiv 1

We report that thyroid hormone (T3) receptor (T3R) can activate the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR). Purified chick T3R-alpha 1 (cT3R-alpha 1) binds as monomers and homodimers to a region in the LTR (nucleotides -104 to -75 [-104/-75]) which contains two tandem NF-kappa B binding sites and to a region (-80/-45) which contains three Sp1 binding sites. In contrast, human retinoic acid receptor alpha (RAR-alpha) and mouse retinoid X receptor beta (RXR-beta) do not bind to these elements. However, RXR-beta binds to these elements as heterodimers with cT3R-alpha 1 and to a lesser extent with RAR-alpha. Gel mobility shift assays also revealed that purified NF-kappa B p50/65 or p50/50 can bind to one but not both NF-kappa B sites simultaneously. Although the binding sites for p50/65, p50/50, and T3R, or Sp1 and T3R, overlap, their binding is mutually exclusive, and with the inclusion of RXR-beta, the major complex is the RXR-beta-cT3R-alpha 1 heterodimer. The NF-kappa B region of the LTR and the NF-kappa B elements from the kappa light chain enhancer both function as T3 response elements (TREs) when linked to a heterologous promoter. The TREs in the HIV-1 NF-kappa B sites appear to be organized as a direct repeat with an 8- or 10-bp gap between the half-sites. Mutations within the NF-kappa B motifs which eliminate binding of cT3R-alpha 1 also abolish stimulation by T3, indicating that cT3R-alpha 1 binding to the Sp1 region does not independently mediate activation by T3. The Sp1 region, however, is converted to a functionally strong TRE by the viral tat factor. These studies indicate that the HIV-1 LTR contains both tat-dependent and tat-independent TREs and reveal the potential for T3R to modulate other genes containing NF-kappa B- and Sp1-like elements. Furthermore, they indicate the importance of other transcription factors in determining whether certain T3R DNA binding sequences can function as an active TRE.

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