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 High-Mobility-Group Protein I Can Modulate Binding of Transcription Factors to the U5 Region of the Human Immunodeficiency Virus Type 1 Proviral Promoter

2000 ◽  
Vol 74 (22) ◽  
pp. 10523-10534 ◽  
Author(s):  
Angus Henderson ◽  
Michael Bunce ◽  
Nicole Siddon ◽  
Raymond Reeves ◽  
David John Tremethick
Keyword(s):  
Human Immunodeficiency Virus ◽  
Transcription Factor ◽  
Dna Binding ◽  
Binding Site ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Binding Sites ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT HMG I/Y appears to be a multifunctional protein that relies on in its ability to interact with DNA in a structure-specific manner and with DNA, binding transcriptional activators via distinct protein-protein interaction surfaces. To investigate the hypothesis that HMG I/Y may have a role in human immunodeficiency virus type 1 (HIV-1) expression, we have analyzed whether HMG I/Y interacts with the 5′ long terminal repeat and whether this interaction can modulate transcription factor binding. Using purified recombinant HMG I, we have identified several high-affinity binding sites which overlap important transcription factor binding sites. One of these HMG I binding sites coincides with an important binding site for AP-1 located downstream of the transcriptional start site, in the 5′ untranslated region at the boundary of a positioned nucleosome. HMG I binding to this composite site inhibits the binding of recombinant AP-1. Consistent with this observation, using nuclear extracts prepared from Jurkat T cells, we show that HMG I (but not HMG Y) is strongly induced upon phorbol myristate acetate stimulation and this induced HMG I appears to both selectively inhibit the binding of basal DNA-binding proteins and enhance the binding of an inducible AP-1 transcription factor to this AP-1 binding site. We also report the novel finding that a component present in this inducible AP-1 complex is ATF-3. Taken together, these results argue that HMG I may play a fundamental role in HIV-1 expression by determining the nature of transcription factor-promoter interactions.

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 Functional Differences between the Long Terminal Repeat Transcriptional Promoters of Human Immunodeficiency Virus Type 1 Subtypes A through G

2000 ◽  
Vol 74 (8) ◽  
pp. 3740-3751 ◽  
Author(s):  
Rienk E. Jeeninga ◽  
Maarten Hoogenkamp ◽  
Mercedes Armand-Ugon ◽  
Michel de Baar ◽  
Koen Verhoef ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Long Terminal Repeat ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Subtype B ◽  
Immunodeficiency Virus ◽  
Ltr Promoter ◽  
Hiv 1 ◽  
Biological Differences

ABSTRACT The current human immunodeficiency virus type 1 (HIV-1) shows an increasing number of distinct viral subtypes, as well as viruses that are recombinants of at least two subtypes. Although no biological differences have been described so far for viruses that belong to different subtypes, there is considerable sequence variation between the different HIV-1 subtypes. The HIV-1 long terminal repeat (LTR) encodes the transcriptional promoter, and the LTR of subtypes A through G was cloned and analyzed to test if there are subtype-specific differences in gene expression. Sequence analysis demonstrated a unique LTR enhancer-promoter configuration for each subtype. Transcription assays with luciferase reporter constructs showed that all subtype LTRs are functional promoters with a low basal transcriptional activity and a high activity in the presence of the viral Tat transcriptional activator protein. All subtype LTRs responded equally well to the Tattrans activator protein of subtype B. This result suggests that there are no major differences in the mechanism of Tat-mediatedtrans activation among the subtypes. Nevertheless, subtype-specific differences in the activity of the basal LTR promoter were measured in different cell types. Furthermore, we measured a differential response to tumor necrosis factor alpha treatment, and the induction level correlated with the number of NF-κB sites in the respective LTRs, which varies from one (subtype E) to three (subtype C). In general, subtype E was found to encode the most potent LTR, and we therefore inserted the core promoter elements of subtype E in the infectious molecular clone of the LAI isolate (subtype B). This recombinant LAI-E virus exhibited a profound replication advantage compared with the original LAI virus in the SupT1 T-cell line, indicating that subtle differences in LTR promoter activity can have a significant impact on viral replication kinetics. These results suggest that there may be considerable biological differences among the HIV-1 subtypes.

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.

scholarly journals Concordant Modulation of Neutralization Resistance and High Infectivity of the Primary Human Immunodeficiency Virus Type 1 MN Strain and Definition of a Potential gp41 Binding Site in gp120

2003 ◽  
Vol 77 (1) ◽  
pp. 560-570 ◽  
Author(s):  
Maria Leavitt ◽  
Eun Ju Park ◽  
Igor A. Sidorov ◽  
Dimiter S. Dimitrov ◽  
Gerald V. Quinnan,
Keyword(s):  
Human Immunodeficiency Virus ◽  
Binding Site ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Binding Sites ◽  
Leucine Zipper ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
High Infectivity

ABSTRACT Efforts to develop a vaccine against human immunodeficiency virus type 1 (HIV-1) are complicated by resistance of virus to neutralization. The neutralization resistance phenotype of HIV-1 has been linked to high infectivity. We studied the mechanisms determining this phenotype using clones of the T-cell-line-adapted (TCLA) MN strain (MN-TCLA) and the neutralization-resistant, primary MN strain (MN-P). Mutations in the amino- and carboxy-terminal halves of gp120 and the carboxy terminus of gp41 contributed to the neutralization resistance, high-infectivity phenotype but depended upon sequences in the leucine zipper (LZ) domain of gp41. Among 23 clones constructed to map the contributing mutations, there was a very strong correlation between infectivity and neutralization resistance (R 2 = 0.81; P < 0.0001). Mutations that distinguished the gp120s of MN-P and MN-TCLA clones were clustered in or near the CD4 and coreceptor binding sites and in regions distant from those binding sites. To test the hypothesis that some of these distant mutations may interact with gp41, we determined which of them contributed to high infectivity and whether those mutations modulated gp120-gp41 association in the context of MN-P LZ sequences. In one clone, six mutations in the amino terminus of gp120, at least four of which clustered closely on the inner domain, modulated infectivity. This clone had a gp120-gp41 association phenotype like MN-P: in comparison to MN-TCLA, spontaneous dissociation was low, and dissociation induced by soluble CD4 binding was high. These results identify a region of the gp120 inner domain that may be a binding site for gp41. Our studies clarify mechanisms of primary virus neutralization resistance.

Sign in / Sign up

Export Citation Format

Share Document