Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human immunodeficiency virus type 1 (HIV-1) isolates from various patients were divided into two major groups, rapid/high and slow/low, according to their replication properties in vitro. Rapid/high isolates grow well in cell lines and induce the formation of syncytia in peripheral blood mononuclear cells. In contrast, slow/low isolates do not replicate in cell lines and rarely induce syncytia in peripheral blood mononuclear cells. To understand the differences in replicative capacity of these isolates, a panel of indicator cell lines was used. These cell lines were generated for sensitive detection of HIV-1 isolates and show characteristics of T-lymphoid or monocytoid cells. As a result of infection, chloramphenicol acetyltransferase expression is activated. Rapid/high viruses activate chloramphenicol acetyltransferase expression in T-cell and monocytoid indicator cell lines, whereas slow/low isolates activate chloramphenicol acetyltransferase expression only in monocytoid cell lines. The block in infection of T-lymphoid cells by the slow/low isolates appears to occur early in the infection cycle, prior to the production of the virally encoded tat protein. HIV-1 isolates can thus be distinguished according to target-cell tropism. Monocyte-derived cells seem to be a more general target for the various HIV-1 isolates.
 ...
PMID:Rapidly and slowly replicating human immunodeficiency virus type 1 isolates can be distinguished according to target-cell tropism in T-cell and monocyte cell lines. 278 83

Human immunodeficiency virus type 1 (HIV-1)-infected subjects show a high incidence of Epstein-Barr virus (EBV) infection. This suggests that EBV may function as a cofactor that affects HIV-1 activation and may play a major role in the progression of AIDS. To test this hypothesis, we generated two EBV-negative human B-cell lines that stably express the EBNA2 gene of EBV. These EBNA2-positive cell lines were transiently transfected with plasmids that carry either the wild type or deletion mutants of the HIV-1 long terminal repeat (LTR) fused to the chloramphenicol acetyltransferase (CAT) gene. There was a consistently higher HIV-1 LTR activation in EBNA2-expressing cells than in control cells, which suggested that EBNA2 proteins could activate the HIV-1 promoter, possibly by inducing nuclear factors binding to HIV-1 cis-regulatory sequences. To test this possibility, we used CAT-based plasmids carrying deletions of the NF-kappa B (pNFA-CAT), Sp1 (pSpA-CAT), or TAR (pTAR-CAT) region of the HIV-1 LTR and retardation assays in which nuclear proteins from EBNA2-expressing cells were challenged with oligonucleotides encompassing the NF-kappa B or Sp1 region of the HIV-1 LTR. We found that both the NF-kappa B and the Sp1 sites of the HIV-1 LTR are necessary for EBNA2 transactivation and that increased expression resulted from the induction of NF-kappa B-like factors. Moreover, experiments with the TAR-deleted pTAR-CAT and with the tat-expressing pAR-TAT plasmids indicated that endogenous Tat-like proteins could participate in EBNA2-mediated activation of the HIV-1 LTR and that EBNA2 proteins can synergize with the viral tat transactivator. Transfection experiments with plasmids expressing the EBNA1, EBNA3, and EBNALP genes did not cause a significant HIV-1 LTR activation. Thus, it appears that among the latent EBV genes tested, EBNA2 was the only EBV gene active on the HIV-1 LTR. The transactivation function of EBNA2 was also observed in the HeLa epithelial cell line, which suggests that EBV and HIV-1 infection of non-B cells may result in HIV-1 promoter activation. Therefore, a specific gene product of EBV, EBNA2, can transactivate HIV-1 and possibly contribute to the clinical progression of AIDS.
 ...
PMID:Epstein-Barr virus nuclear antigen 2 transactivates the long terminal repeat of human immunodeficiency virus type 1. 838 79

Human immunodeficiency virus type 1 (HIV-1) variants resistant to protease inhibitors have been shown to contain a mutation in the p1/p6 Gag precursor cleavage site. At the messenger RNA level, this mutation generates a U UUU UUU sequence that is reminiscent of the U UUU UUA sequence required for ribosomal frameshifting and Gag-Pol synthesis. To test whether the p1/p6 cleavage site mutation was generating a novel frameshift site, HIV sequences were inserted in translation vectors containing a chloramphenicol acetyltransferase (CAT) reporter gene requiring -1 frameshifting for expression. All sequences containing the original HIV frameshift site supported the synthesis of CAT but expression was increased 3- to 11-fold in the presence of the mutant p1/p6 sequence. When the original frameshift site was abolished by mutation, expression remained unchanged when using constructs containing the mutant p1/p6 sequence, whereas it was decreased 2- to 4.5-fold when using wild-type p1/p6 constructs. Similarly, when introduced into HIV molecular clones, the p1/p6 mutant sequence supported Gag-Pol synthesis and protease activity in the absence of the original frameshift site, indicating that this sequence could also promote ribosomal frameshifting in virus-expressing cells.
 ...
PMID:Novel Gag-Pol frameshift site in human immunodeficiency virus type 1 variants resistant to protease inhibitors. 962 Oct 79

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-kappaB binding sites. The variant enhancer sequence demonstrated a severe loss of NF-kappaB binding in protein binding assays. Interestingly, we observed a new binding activity that is specific for the variant NF-kappaB sequence and is present in the nuclear extract of unstimulated cells that lack NF-kappaB. These results suggest that inactivation of the NF-kappaB 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-kappaB protein. These results suggest that GABP potentiates Tat-mediated activation of LTR transcription and viral replication in some cell types. Conversion of an NF-kappaB 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.
 ...
PMID:Evolution of the human immunodeficiency virus type 1 long terminal repeat promoter by conversion of an NF-kappaB enhancer element into a GABP binding site. 988 38

Human immunodeficiency virus type 1 (HIV-1) gene expression and replication is highly dependent on and modulated by interactions between viral and host cellular factors. Tat protein, encoded by one of the HIV-1 regulatory genes, tat, is essential for HIV-1 gene expression. A number of host cellular factors have been shown to interact with Tat in this process. During our attempts to determine the molecular mechanisms of Tat interaction with brain cells, we isolated a cDNA clone that encodes a novel Tat-interacting protein of 110 kDa or Tip110 from a human fetal brain cDNA library. GenBank BLAST search revealed that Tip110 was almost identical to a previously cloned KIAA0156 gene with unknown functions. In vivo binding of Tip110 with Tat was confirmed by immunoprecipitation and Western blotting, in combination with mutagenesis. The yeast three-hybrid RNA-protein interaction assay indicated no direct interaction of Tip110 with Tat transactivating response element RNA. Nevertheless, Tip110 strongly synergized with Tat on Tat-mediated chloramphenicol acetyltransferase reporter gene expression and HIV-1 virus production, whereas down-modulation of constitutive Tip110 expression inhibited HIV-1 virus production. Northern blot analysis showed that Tip110 mRNA was expressed in a variety of human tissues and cells. Moreover, digital fluorescence microscopic imaging revealed that Tip110 was expressed exclusively in the nucleus, and within a nuclear speckle structure that has recently been described for human cyclin T and CDK9, two critical components for Tat transactivation function on HIV-1 long terminal repeat promoter. Taken together, these data demonstrate that Tip110 regulates Tat transactivation activity through direct interaction, and suggest that Tip110 is an important cellular factor for HIV-1 gene expression and viral replication.
 ...
PMID:HIV-1 Tat protein-mediated transactivation of the HIV-1 long terminal repeat promoter is potentiated by a novel nuclear Tat-interacting protein of 110 kDa, Tip110. 1195 60

Human immunodeficiency virus type 1 (HIV-1) replication requires active nuclear export of unspliced and incompletely spliced HIV-1 RNA transcripts. This process is evolutionally made possible by expression of HIV-1 Rev, one of the three HIV-1 proteins encoded by completely spliced HIV-1 RNAs. Evidence has accumulated to suggest that Sam68 plays an important role in HIV-1 replication through HIV-1 Rev protein. In the present study, we further examined the structure-function relationship of Sam68 protein in relation to HIV-1 replication. We identified a Sam68 domain located between aa269 and aa321 to be involved in the HIV-inhibitory effects of Sam68 dominant negative mutants lacking the nuclear localization signal (NLS). Deletion of this domain abrogated inhibition of HIV-1 replication by these mutants. HIV-1 Rev protein appeared to mediate the HIV-inhibitory effects of these mutants and by this domain, as assessed by Rev-dependent chloramphenicol acetyltransferase reporter gene assay, in trans rev-defective HIV-1 complementation assay, and RNase protection assay. The HIV-inhibitory mutants containing this domain were further found to have diminished binding affinity to the wild-type Sam68 and to be associated with cytoplasmic retention of exclusively nuclear localized wild type Sam68. Taken together, these results further ascertain the important role of Sam68 in HIV-1 Rev function and viral replication, and suggest that the HIV-inhibitory effects of Sam68 dominant negative mutants directly result from their binding to endogenous Sam68 and their interference with nuclear localization of endogenous Sam68.
 ...
PMID:Requirement of an additional Sam68 domain for inhibition of human immunodeficiency virus type 1 replication by Sam68 dominant negative mutants lacking the nuclear localization signal. 1623 70