Human immunodeficiency virus type 1 long terminal repeat quasispecies differ in basal transcription and nuclear factor recruitment in human glial cells and lymphocytes

Abstract

The generation of genomic diversity during the course of infection has the potential to affect all aspects of HIV-1 replication, including expression of the proviral genome. To gain a better understanding of the impact of long terminal repeat (LTR) sequence diversity on LTR-directed gene expression in cells of the central nervous system (CNS) and immune system, we amplified and cloned LTRs from proviral DNA in HIV-1-infected peripheral blood. Sequence analysis of nineteen LTRs cloned from 2 adult and 3 pediatric patients revealed an average of 33 nucleotide changes (with respect to the sequence of the LAI LTR) within the 455-bp U3 region. Transient expression analyses in cells of neuroglial and lymphocytic origin demonstrated that some of these LTRs had activities which varied significantly from the LAI LTR in U-373 MG cells (an astrocytoma cell line) as well as in Jurkat cells (a CD4-positive lymphocyte cell line). While LTRs which demonstrated the highest activities in U-373 MG cells also yielded high activities in Jurkat cells, the LTRs were generally more active in Jurkat cells when compared to the LAI LTR. Differences in LTR sequence also resulted in differences in transcription factor recruitment to cis-acting sites within the U3 region of the LTR, as demonstrated by electrophoretic mobility shift assays. In particular, naturally occurring sequence variation impacted transcription factor binding to an activating transcription factor/cAMP response element binding (ATF/CREB) binding site (located between the LEF-1 and distal NF-kappaB transcription factor binding sites) that we identified in previous studies of the HIV-1 LTR. These findings suggest that LTR sequence changes can significantly affect basal LTR function and transcription factor recruitment, which may, in turn, alter the course of viral replication in cells of CNS and immune system origin.

Pertussis Toxin B-Oligomer Suppresses IL-6 Induced HIV-1 and Chemokine Expression in Chronically Infected U1 Cells via Inhibition of Activator Protein 1

“…In this regard, only AP-1 expressed in glial and HeLa cells, but not in Jurkat and neuronal cells, was reported to interact with the HIV-1 LTR (68). These findings suggest that distinct forms of this transcription factor possess different binding capacities for HIV DNA as well as differential potency in modulating HIV transcription (68,69). Indeed, certain members of the Jun and Fos families may exert suppressive effects on viral transcription, as previously described with cAMP-responsive element (CRE)/ATF in Jurkat and HeLa cells (70).…”

Interaction between CCAAT/Enhancer Binding Protein and Cyclic AMP Response Element Binding Protein 1 Regulates Human Immunodeficiency Virus Type 1 Transcription in Cells of the Monocyte/Macrophage Lineage

“…1A). Previous studies have indicated that sequence variation at the ATF/CREB site impacts ATF/CREB protein binding and HIV-1 LTR activity (22,23). Furthermore, numerous reports have described synergistic transactivation of different promoters by proteins from the ATF/CREB and C/EBP families (33,35,41).…”

“…1A. In this report, the functional properties of C/EBP binding site I are examined along with the impact of a directly adjacent ATF/CREB site (22,23) on the activity of this NF-B-proximal cis-acting element relevant to LTR-directed transcription in cells of the monocyte/macrophage lineage.…”

“…Specifically, other protein families that commonly interact with C/EBP proteins include Sp, nuclear factor kappa B (NF-B), and activating transcription factor/cyclic AMP response element (CRE) binding protein (ATF/CREB) (16,22,23). For example C/EBP ␣ has been implicated as an important factor involved in the liverspecific, cyclic AMP responsiveness of the phosphoenolpyruvate carboxykinase (PEPCK) promoter (33).…”

Impact of Naturally Occurring Genetic Variation in the HIV-1 LTR TAR Region and Sp Binding Sites on Tat-Mediated Transcription

“…The enhancer region is located upstream of the GC box array and consists of two tandem nuclear factor-κB (NF-κB) binding sites. The modulatory region, located further upstream of the NF-κB sites, includes binding sites for CCAAT/enhancer binding proteins (C/EBP), activating transcription factor/cyclic AMP response element binding (ATF/CREB) factors, lymphocyte enhancer factor (LEF-1), nuclear factor of activated T cells (NFAT), and a number of other transcription factors [3,4].…”