Cytoplasmic IkappaBalpha increases NF-kappaB-independent transcription through binding to histones deacetylases (HDAC1 and HDAC3)

in Journal of Biological Chemistry (2003)

Synergistic activation of human immunodeficiency virus type 1 promoter activity by NF-kappa B and inhibitors of deacetylases: Potential perspectives for the development of therapeutic strategies

in Journal of Virology (2002), 76(21), 11091-11103

The transcription factor NF-kappaB plays a central role in the human immunodeficiency virus type 1 (HIV-1) activation pathway. HIV-1 transcription is also regulated by protein acetylation, since treatment ... [more ▼]

The transcription factor NF-kappaB plays a central role in the human immunodeficiency virus type 1 (HIV-1) activation pathway. HIV-1 transcription is also regulated by protein acetylation, since treatment with deacetylase inhibitors such as trichostatin A (TSA) or sodium butyrate (NaBut) markedly induces HIV-1 transcriptional activity of the long terminal repeat (LTR) promoter. Here, we demonstrate that TSA (NaBut) synergized with both ectopically expressed p50/p65 and tumor necrosis factor alpha/SF2 (TNF)-induced NF-kappaB to activate the LTR. This was confirmed for LTRs from subtypes A through G of the HIV-1 major group, with a positive correlation between the number Of kappaB sites present in the LTRs and the amplitude of the TNF-TSA synergism. Mechanistically, TSA (NaBut) delayed the cytoplasmic recovery of the inhibitory protein IkappaBalpha. This coincided with a prolonged intranuclear presence and DNA binding activity of NF-kappaB. The physiological relevance of the TNF-TSA (NaBut) synergism was shown on HIV-1 replication in both acutely and latently HIV-infected cell lines. Therefore, our results open new therapeutic strategies aimed at decreasing or eliminating the pool of latently HIV-infected reservoirs by forcing viral expression. [less ▲]

CIKS, a connection to Ikappa B kinase and stress-activated protein kinase.

in Proceedings of the National Academy of Sciences of the United States of America (2000), 97(19), 10494-10499

Pathogens, inflammatory signals, and stress cause acute transcriptional responses in cells. The induced expression of genes in response to these signals invariably involves transcription factors of the NF ... [more ▼]

Pathogens, inflammatory signals, and stress cause acute transcriptional responses in cells. The induced expression of genes in response to these signals invariably involves transcription factors of the NF-kappaB and AP-1/ATF families. Activation of NF-kappaB factors is thought to be mediated primarily via IkappaB kinases (IKK), whereas that of AP-1/ATF can be mediated by stress-activated protein kinases (SAPKs; also named Jun kinases or JNKs). IKKalpha and IKKbeta are two catalytic subunits of a core IKK complex that also contains the regulatory subunit NEMO (NF-kappaB essential modulator)/IKKgamma. The latter protein is essential for activation of the IKKs, but its mechanism of action is not known. Here we describe the molecular cloning of CIKS (connection to IKK and SAPK/JNK), a previously unknown protein that directly interacts with NEMO/IKKgamma in cells. When ectopically expressed, CIKS stimulates IKK and SAPK/JNK kinases and it transactivates an NF-kappaB-dependent reporter. Activation of NF-kappaB is prevented in the presence of kinase-deficient, interfering mutants of the IKKs. CIKS may help to connect upstream signaling events to IKK and SAPK/JNK modules. CIKS could coordinate the activation of two stress-induced signaling pathways, functions reminiscent of those noted for tumor necrosis factor receptor-associated factor adaptor proteins. [less ▲]

Ikappab-Alpha Enhances Transactivation by the Hoxb7 Homeodomain-Containing Protein

in Journal of Biological Chemistry (1999), 274(9), 5318-25

Combinatorial interactions between distinct transcription factors generate specificity in the controlled expression of target genes. In this report, we demonstrated that the HOXB7 homeodomain-containing ... [more ▼]

Combinatorial interactions between distinct transcription factors generate specificity in the controlled expression of target genes. In this report, we demonstrated that the HOXB7 homeodomain-containing protein, which plays a key role in development and differentiation, physically interacted in vitro with IkappaB-alpha, an inhibitor of NF-kappaB activity. This interaction was mediated by the IkappaB-alpha ankyrin repeats and C-terminal domain as well as by the HOXB7 N-terminal domain. In transient transfection experiments, IkappaB-alpha markedly increased HOXB7-dependent transcription from a reporter plasmid containing a homeodomain consensus-binding sequence. This report therefore showed a novel function for IkappaB-alpha, namely a positive regulation of transcriptional activation by homeodomain-containing proteins. [less ▲]

Molecular Cloning of a Mutated Hoxb7 Cdna Encoding a Truncated Transactivating Homeodomain-Containing Protein

in Journal of Cellular Biochemistry (1998), 71(1), 46-54

Homeodomain-containing proteins regulate, as transcription factors, the coordinated expression of genes involved in development, differentiation, and malignant transformation. We report here the molecular ... [more ▼]

Homeodomain-containing proteins regulate, as transcription factors, the coordinated expression of genes involved in development, differentiation, and malignant transformation. We report here the molecular cloning of a mutated HOXB7 transcript encoding a truncated homeodomain-containing protein in MCF7 cells. This is a new example of mutation affecting the coding region of a HOX gene. In addition, we detected two HOXB7 transcripts in several breast cell lines and demonstrated that both normal and mutated alleles were expressed at the RNA level in MCF7 cells as well as in a variety of breast tissues and lymphocytes, suggesting that a truncated HOXB7 protein might be expressed in vivo. Using transient co-transfection experiments, we demonstrated that both HOXB7 proteins can activate transcription from a consensus HOX binding sequence in breast cancer cells. Our results provide evidence that HOXB7 protein has transcription factor activity in vivo and that the two last amino acids do not contribute to this property. [less ▲]

Detection of Hoxa1 Expression in Human Breast Cancer

in Biochemical and Biophysical Research Communications (1996), 222(2), 292-7

Homeodomain-containing proteins are transcription factors that regulate the coordinated expression of multiple genes involved in development, differentiation and malignant transformation. To better ... [more ▼]

Homeodomain-containing proteins are transcription factors that regulate the coordinated expression of multiple genes involved in development, differentiation and malignant transformation. To better understand the role played by these proteins in breast cancer cells, we demonstrate, using semi-quantitative RT-PCR experiments, that progestin induces HOXA1 mRNAs in MCF7 cells. This is the first evidence of regulation of a HOX gene by steroids. Moreover, we detected HOXA1 expression in a variety of human breast cancer lesions, suggesting that HOXA1 may be required for the establishment of breast cancer cells phenotype. We propose that HOXA1 gene could be one of the orchestrators that regulate breast epithelial cell differentiation and that alteration of HOXA1 expression could play a role in breast cancer progression. [less ▲]

Retinoic Acid Induces Three Newly Cloned Hoxa1 Transcripts in Mcf7 Breast Cancer Cells

in Biochemical and Biophysical Research Communications (1995), 215(2), 713-20

Coordinated expression of genes involved in development, differentiation and malignant transformation is regulated by transcription factors including homeodomain-containing proteins. However, most of ... [more ▼]

Coordinated expression of genes involved in development, differentiation and malignant transformation is regulated by transcription factors including homeodomain-containing proteins. However, most of their cDNA sequences are still unknown. We report here the molecular characterization of three newly cloned HOXA1 transcripts from human breast cancer cells. In addition, we provide evidence that these alternatively spliced transcripts encode one homeodomain-containing protein and two products lacking the conserved DNA-binding domain. Moreover, we demonstrate that all three HOXA1 transcripts are induced by retinoic acid in MCF7 cells. Taken together, our results suggest that HOXA1 gene may be a key element in the establishment of the breast cancer cell phenotype. [less ▲]

Homeobox Genes: Potential Candidates for the Transcriptional Control of the Transformed and Invasive Phenotype

in Biochemical Pharmacology (1994), 47(1), 137-43

The transformation of a cell and the acquisition of the invasive and metastatic phenotype result from the activation of a group of complex cellular processes rather than from the effect of a single gene ... [more ▼]

The transformation of a cell and the acquisition of the invasive and metastatic phenotype result from the activation of a group of complex cellular processes rather than from the effect of a single gene product. It is likely that the coordination of the multiple genes involved in malignancy is under the control of a few genes that act as master genes or orchestrator genes. The latter probably code for transcription factors that control the genetic program for tumor invasion and metastasis. Homeobox genes are a family of transcription factors that contain a 183 bp highly conserved nucleotide sequence coding for a 61 amino acid domain that binds specifically to DNA. First discovered in Drosophila as genes controlling segmentation and segment identity, homeobox genes have since been identified in many other species including nematodes, frog, mouse and human. There is strong support for the suggestion that homeobox genes play a key role in development and differentiation. In humans, there are 38 homeobox genes organized in four clusters that are localized on chromosomes 2, 7, 12 and 17. The specific functions of each of these genes are generally unknown. Alterations in expression of several homeobox genes have been reported in a variety of malignant lesions, suggesting that they could play a role in the development of cancer. Using reverse transcriptase reaction coupled with polymerase chain reaction and degenerate oligonucleotides corresponding to the 5' and 3' ends of the highly conserved homeodomain, we amplified 130 bp cDNA fragments from the human breast cancer cell line MCF7 that were subsequently cloned into pBluescript vector. Sequencing of the clones, resulted in the identification of the homeodomains of four different human homeobox genes: HOXB6, HOXA1, HOXA10 and HOXC6. Further studies should determine the specific role of these four homeobox genes in the development and progression of human breast cancer and potentially determine if they might be good targets for gene therapy. [less ▲]