Related subunits of NF-kappa B map to two distinct loci associated with translocations in leukemia, NFKB1 and NFKB2

High levels of p105 (NFKB1) and p100 (NFKB2) proteins in HPV16-transformed keratinocytes: role of E6 and E7 oncoproteins

We have previously shown that functional components of the NF-kappaB signaling pathway are up-regulated and sequestered in the cytoplasm of human papillomavirus 16 (HPV16)-transformed cell lines leading to a reduced activity of NF-kappaB. In this study, we examined the expression of the NF-kappaB precursors p100 and p105 in keratinocytes transformed or not by HPV16. Western immunoblotting experiments demonstrated high levels of p100 and p105 proteins not only in HPV16+ cervical carcinoma-derived keratinocytes but also in keratinocytes stably transfected by HPV16 E6 or E7 oncogenes. Moreover, p100 and p105 proteins were predominantly cytoplasmic and nuclear in keratinocytes expressing E7 and E6, respectively. A predominantly cytoplasmic localization of E7 protein was also detected in all keratinocytes expressing E7. Our results suggest that HPV16 E6 and E7 proteins modulate the expression and the subcellular localization of p100 and p105 NF-kappaB precursors.

Functions of NF-kappaB1 and NF-kappaB2 in immune cell biology

Two members of the NF-kappaB (nuclear factor kappaB)/Rel transcription factor family, NF-kappaB1 and NF-kappaB2, are produced as precursor proteins, NF-kappaB1 p105 and NF-kappaB2 p100 respectively. These are proteolytically processed by the proteasome to produce the mature transcription factors NF-kappaB1 p50 and NF-kappaB2 p52. p105 and p100 are known to function additionally as IkappaBs (inhibitors of NF-kappaB), which retain associated NF-kappaB subunits in the cytoplasm of unstimulated cells. The present review focuses on the latest advances in research on the function of NF-kappaB1 and NF-kappaB2 in immune cells. NF-kappaB2 p100 processing has recently been shown to be stimulated by a subset of NF-kappaB inducers, including lymphotoxin-beta, B-cell activating factor and CD40 ligand, via a novel signalling pathway. This promotes the nuclear translocation of p52-containing NF-kappaB dimers, which regulate peripheral lymphoid organogenesis and B-lymphocyte differentiation. Increased p100 processing also contributes to the malignant phenotype of certain T- and B-cell lymphomas. NF-kappaB1 has a distinct function from NF-kappaB2, and is important in controlling lymphocyte and macrophage function in immune and inflammatory responses. In contrast with p100, p105 is constitutively processed to p50. However, after stimulation with agonists, such as tumour necrosis factor-alpha and lipopolysaccharide, p105 is completely degraded by the proteasome. This releases associated p50, which translocates into the nucleus to modulate target gene expression. p105 degradation also liberates the p105-associated MAP kinase (mitogen-activated protein kinase) kinase kinase TPL-2 (tumour progression locus-2), which can then activate the ERK (extracellular-signal-regulated kinase)/MAP kinase cascade. Thus, in addition to its role in NF-kappaB activation, p105 functions as a regulator of MAP kinase signalling.

Increased expression of NF-kappa B subunits in human pancreatic cancer cells

BACKGROUND

Activation of NF-kappa B-dependent antiapoptotic genes may factor in the chemoresistance of pancreatic cancer. It is not known whether NF-kappa B subunit composition changes during oncogenesis and regulates overall NF-kappa B activation. We compared the relative expression of NF-kappa B subunits with nuclear activation of p65 between variably differentiated pancreatic cancer cells.

MATERIALS AND METHODS

Proliferating human pancreatic cancer cells (PANC-1, BxPC-3) and nonmalignant intestinal cells (FHS 74 Int) were harvested. Baseline expression of NF-kappa B subunits (p65, p52, p50, c-Rel) and its inhibitor I kappa B-alpha were determined by Western blot. Nuclear NF-kappa B p65 activity was measured by ELISA. Results were analyzed by ANOVA (P < 0.05) and Tukey's HSD for pairwise comparisons when appropriate (P < 0.05).

RESULTS

Constitutive expression of NF-kappa B subunits was detected in proliferating, intestinal cells (FHS 74 Int). Both cytoplasmic (I kappa B-alpha, p50, p52, p65) and nuclear (p50, p52, p65, c-Rel) NF-kappa B subunits were significantly increased in both PANC-1 and BxPC-3 cells compared to FHS 74 Int. While nuclear p65 subunit levels were similarly elevated, actual p65 activity was only significantly greater in PANC-1 cells compared to either BxPC-3 or FHS 74 Int (P < 0.05).

CONCLUSIONS

Compared to nonmalignant proliferating intestinal cells, these pancreatic cancer cell lines have increased levels of NF-kappa B subunits. Actual nuclear NF-kappa B activity, however, appears to correlate more with degree of tumor differentiation than with NF-kappa B subunit expression.

Nuclear factor-kappaB modulation as a therapeutic approach in hematologic malignancies

Nuclear factor-kappaB (NF-kappaB) is a collective term that refers to a small class of dimeric transcription factors for a number of genes, including growth factors, angiogenesis modulators, cell-adhesion molecules, and antiapoptotic factors. Although most NF-kappaB proteins promote transcription, some act as inactivating or repressive complexes. The most common p50-RelA (p65) dimer known "specifically" as NF-kappaB, is relatively abundant, controls the expression of numerous genes, and exists as an inactive cytoplasmic complex bound to inhibitory proteins of the NF-kappaB inhibitor (IkappaB) family. The inactive NF-kappaB-IkappaB complex is activated by a variety of stimuli, including proinflammatory cytokines, mitogens, growth factors, and stress-inducing agents. The release of NF-kappaB facilitates its translocation to the nucleus, where it promotes cell survival by initiating the transcription of genes encoding stress-response enzymes, cell-adhesion molecules, proinflammatory cytokines, and antiapoptotic proteins. Constitutive activation of NF-kappaB in the nucleus is observed in some hematologic disorders. With the recent approval of bortezomib for patients with advanced multiple myeloma, NF-kappaB modulation is likely to be a therapeutic endeavor of increasing interest in coming years.

Screening of genes trans-regulated by NS5ATP9 with cDNA microarray assay

AIM: To screen the genes trans-regulated by NS5ATP9 with cDNA microarray assay.

METHODS: The recombined expressive plasmid pcDNA 3.1(-)-NS5ATP9 was constructed, and HepG2 cells were transfected. Total mRNA was isolated from the HepG2 cells transfected with pcDNA3.1(-) and pcDNA3.1(-)-NS5ATP9, respectively. cDNA microarray was employed for detecting and analyzing of mRNA from both HepG2 cells transfected.

RESULTS: From the microarray assay, 3 genes were found up-regulated, and 13 genes down-regulated. Their encoding proteins were involved in cell signal transduction, cell proliferation, cell apoptosis and differentiation.

CONCLUSION: cDNA microarray technology is successfully used to screen diversity genes expressed by NS5ATP9 in HepG2 cells, which brings some new clues for the study of the function of NS5ATP9.

Phosphorylation of NF-kappaB proteins by cyclic GMP-dependent kinase. A noncanonical pathway to NF-kappaB activation

The transcription factor NF-kappaB is activated in cellular stress responses. This requires rapid regulation of its function, which is accomplished, in part, by various modes of phosphorylation. Even though diverse DNA binding subunits of NF-kappaB proteins may transactivate from distinct recognition sequences, the differential regulation of transcription from the large number of NF-kappaB responsive sites in various gene promoters and enhancers has been incompletely understood. The cyclic GMP-dependent kinase (PKG) is an important mediator of signal transduction that may induce gene expression through cAMP response element binding protein (CREB) and through other, yet undefined, mechanisms. We have previously characterized a signal transduction pathway that leads to activation-induced cell death in T-lymphocytes and involves the activation of PKG. Here we demonstrate that the NF-kappaB proteins p65, p49 (also called p52), and p50 are specific substrates for this kinase. PKG dose-dependently increases the transactivating activity of p65 from the NF-kappaB consensus sequence. It also mediates dose-dependently an increase in transcriptional activity by p49 or p50 from a unique CCAAT/enhance binding protein (C/EBP)-associated NF-kappaB site, but not from the consensus site. Phosphorylation of p65, p50, or p49 does not alter their subcellular distribution. Because the release of cytosolic p65/p50 heterodimers into the nucleus is by itself insufficient to differentiate all the numerous NF-kappaB promoter sequences, phosphorylation of the DNA-binding subunits reveals a form of differential regulation of NF-kappaB activity and it implies a novel pathway for PKG-induced gene transcription. These observations may bear on mechanisms of programmed cell death in T-lymphocytes. They may also be relevant to ongoing efforts to induce cancer cell apoptosis through activation of PKG.

p105.Ikappa Bgamma and prototypical Ikappa Bs use a similar mechanism to bind but a different mechanism to regulate the subcellular localization of NF-kappa B

p105, also known as NF-kappaB1, is an atypical IkappaB molecule with a multi-domain organization distinct from other prototypical IkappaBs, like IkappaBalpha and IkappaBbeta. To understand the mechanism by which p105 binds and inhibits NF-kappaB, we have used both p105 and its C-terminal inhibitory segment known as IkappaBgamma for our study. We show here that one IkappaBgamma molecule binds to NF-kappaB dimers wherein at least one NF-kappaB subunit is p50. We suggest that the obligatory p50 subunit in IkappaBgamma.NF-kappaB complexes is equivalent to the N-terminal p50 segment in all p105.NF-kappaB complexes. The nuclear localization signal (NLS) of the obligatory p50 subunit is masked by IkappaBgamma, whereas the NLS of the nonobligatory NF-kappaB subunit is exposed. Thus, the global binding mode of all IkappaB.NF-kappaB complexes seems to be similar where one obligatory (or specific) NF-kappaB subunit makes intimate contact with IkappaB and the nonobligatory (or nonspecific) subunit is bound primarily through its ability to dimerize. In the case of IkappaBalpha and IkappaBbeta, the specific NF-kappaB subunit in the complex is p65. In contrast to IkappaBalpha.NF-kappaB complexes, where the exposed NLS of the nonspecific subunit imports the complex to the nucleus, p105.NF-kappaB and IkappaBgamma.NF-kappaB complexes are cytoplasmic. We show that the death domain of p105 (also of IkappaBgamma) is essential for the cytoplasmic sequestration of NF-kappaB by p105 and IkappaBgamma. However, the death domain does not mask the exposed NLS of the complex. We also demonstrate that the death domain alone is not sufficient for cytoplasmic retention and instead functions only in conjunction with other parts in the three-dimensional scaffold formed by the association of the ankyrin repeat domain (ARD) and NF-kappaB dimer. We speculate that additional cytoplasmic protein(s) may sequester the entire p105.NF-kappaB complex by binding through the death domain and other segments, including the exposed NLS.

Nuclear transcription factor-kappaB as a target for cancer drug development

Nuclear factor kappa B (NF-kappaB) is a family of inducible transcription factors found virtually ubiquitously in all cells. Since its discovery by Sen and Baltimore in 1986, much has been discovered about its mechanisms of activation, its target genes, and its function in a variety of human diseases including those related to inflammation, asthma, atherosclerosis, AIDS, septic shock, arthritis, and cancer. Due to its role in a wide variety of diseases, NF-kappaB has become one of the major targets for drug development. Here, we review our current knowledge of NF-kappaB, the possible mechanisms of its activation, its potential role in cancer, and various strategies being employed to target the NF-kappaB signaling pathway for cancer drug development.

Karyotypic dissection of Hodgkin's disease cell lines reveals ectopic subtelomeres and ribosomal DNA at sites of multiple jumping translocations and genomic amplification

Although the neoplastic significance of the chromosome changes widespread in Hodgkin's disease (HD) remains obscure, a distinct cytogenetic picture has emerged combining aneuploidy with structural rearrangements clustered at certain breakpoints. Notably absent are the recurrent chromosome translocations which distinguish other hematopoietic neoplasms and serve as clues to underlying oncogene alterations. The paucity of neoplastic cells in HD biopsies hinders detailed chromosome analysis. As an alternative, we investigated a panel of well characterized cell lines by classical and molecular cytogenetics, using single-gene and subtelomeric probes, including three autologous HD examples (HDLM-1/2/3) analyzed by 'spectral karyotyping' - the first complete HD karyotype to be documented. Although complex, most rearrangements in HDLM cells arose in vivo and included few rare but many typical HD breakpoints, notably at the r(ibosomal)DNA regions. Two types of genomic rearrangement involving DNA repeats were conspicuous: insertion and genomic amplification/coamplification of rDNA-the first genomic rDNA rearrangements to be reported in a tumor cell, and the first example of multiple 'jumping translocations' (JT). Of four subtelomeric microsatellite repeats tested in HDLM cells, three exhibited interstitial sites at JT, of which two (at 5qter and 9pter) were respectively associated with deletion of the 5q31-32 myeloid region, and coamplification of a recently described HD-recurrent amplicon at 9p2 together with transcriptionally silent rDNA. Altogether, three out of four HD cell lines carried interstitial 9p subtelomeres and rDNA rearrangements. Taken together, these data suggest tumorigenic rearrangements may be facilitated by 'hitchhiking' along with mobile DNA repeat sequences which may target gene rearrangement at 9p in HD. Southern analysis of parallel rearrangements within rDNA intergenic spacers in HDLM cells highlighted several at, or near, retroposons. As well as validating HD cell lines as cytogenetic models, and resources for identifying genes rearranged in HD, our findings warrant further investigation of the roles of DNA repeat sequences, notably subtelomeric microsatellites, rDNA spacer sequences and retroposons as facilitators and markers of tumor-gene rearrangement.

Normal structure of NFKB2, C-REL and BCL-3 gene loci in lymphoproliferative and myeloproliferative disorders

NF-kappaB/rel transcription factors are crucial regulators of development, differentiation and apoptosis of both lymphoid and myeloid lineages. There is increasing evidence for an involvement of NF-kappaB/rel proteins in lymphomagenesis and resistance of lymphoid tumors to the induction of apoptosis. Structural alterations of the NF-kappaB/rel genes NFkappaB2, c-rel and bcl-3 have been shown to result in increased NF-kappaB/rel activity. Because we observed strong constitutive NF-kappaB/rel binding activity in chronic lymphocytic leukemia of the B-cell type (B-CLL) which may contribute to resistance against cytotoxic drugs we studied the genomic organisation of NFkappaB2, c-rel and bcl-3 gene loci in a panel of lymphoproliferative disorders (n=81) with an emphasis on B-CLL (n=47). The method of genomic Southern blotting using cDNAs of the respective genes was used. In spite of the role of NF-kappaB/rel in myeloid maturation there is no data available as to the occurrence of NF-kappaB/rel rearrangements in chronic myeloproliferative syndromes (cMPS). For this reason we included a small panel of cMPS patients (n=16). Southern Blotting revealed a germline configuration of NFkappaB2, c-rel and bcl-3 loci in all NHL and cMPS patients examined. Our results demonstrate that structural alterations of NFkappaB2, c-rel and bcl-3 genes at the Southern Blotting level are rare events that do not contribute to lymphoid or myeloid transformation in the majority of NHL or cMPS patients.

Characterization of the murine homolog of C1qR(P): identical cellular expression pattern, chromosomal location and functional activity of the human and murine C1qR(P)

Human C1qR(P) is a highly glycosylated transmembrane protein that is the human C1q receptor/receptor component that in vitro mediates enhancement of Fc- and C3b-mediated phagocytosis. A human genomic clone and a murine genomic clone that is 73% identical in sequence with the coding region for human C1qR(P) cDNA have been isolated. Chromosomal localization of the human and murine gene demonstrates that these genes are syntenic. Murine cell lines of diverse myeloid origins are shown to respond to interaction of C1q with the enhancement of phagocytosis similar to that seen previously in human peripheral blood monocytes. Northern blot, RT-PCR, Western blot and FACS analyses demonstrated that mC1qR(P) is expressed in these murine myeloid cell lines, but not in a mouse epithelial cell line, similar to the cell type expression of the human gene product. A polyclonal antibody to a peptide sequence common to the deduced sequence from the both murine and human C1qR(P) inhibited the enhancement of phagocytosis response to C1q when cells were permeabilized to permit access of the antibody to the intracellular milieu. These data support the postulate that the identified murine and human genes are homologs, confirm the previously predicted intracellular location of the C-terminus of the molecule, and indicates the necessary role of this intracellular domain in transducing the signal that leads to enhancement of phagocytic function.

Aberrant rel/nfkb genes and activity in human cancer

Rel/NF-kappaB transcription factors are key regulators of immune, inflammatory and acute phase responses and are also implicated in the control of cell proliferation and apoptosis. Remarkable progress has been made in understanding the signal transduction pathways that lead to the activation of Rel/NF-kappaB factors and the consequent induction of gene expression. Evidence linking deregulated Rel/NF-kappaB activity to oncogenesis in mammalian systems has emerged in recent years, consistent with the acute oncogenicity of the viral oncoprotein v-Rel in animal models. Chromosomal amplification, overexpression and rearrangement of genes coding for Rel/NF-kappaB factors have been noted in many human hematopoietic and solid tumors. Persistent nuclear NF-kappaB activity was also described in several human cancer cell types, as a result of constitutive activation of upstream signaling kinases or mutations inactivating inhibitory IkappaB subunits. Studies point to a correlation between the activation of cellular gene expression by Rel/NF-kappaB factors and their participation in the malignant process. Experiments implicating NF-kappaB in the control of the apoptotic response also support a role in oncogenesis and in the resistance of tumor cells to chemotherapy. This review focuses on the status of the rel, nfkb and ikb genes and their activity in human tumors and their association with the onset or progression of malignancies.

Overexpression of urokinase-type plasminogen activator in pancreatic adenocarcinoma is regulated by constitutively activated RelA

The Rel/NF-kappaB transcription factors regulate the expression of many genes. The activity of RelA, a member of the Rel/NF-kappaB transcription factor family, is constitutively activated in the majority of pancreatic adenocarcinomas and cell lines. We report that the urokinase-type plasminogen activator (uPA), one of the critical proteases involved in tumor invasion and metastasis, is overexpressed in pancreatic tumor cells and its overexpression is induced by constitutive RelA activity. The uPA promoter contains an NF-kappaB binding site that directly mediates the induction of uPA expression by RelA. Expression of a dominant-negative IkappaBalpha mutant inhibits kappaB site-dependent transcriptional activation of a uPA promoter-CAT reporter gene. Treating the pancreatic tumor cell lines with the known NF-kappaB inhibitors, dexamethasone and n-tosylphenyalanine chloromethyl ketone (TPCK), abolishes constitutive RelA activity and uPA overexpression. These results show that uPA is one of the downstream target genes induced by constitutively activated RelA in human pancreatic tumor cells, and suggests that constitutive RelA activity may play a critical role in tumor invasion and metastasis. Inhibition of constitutive RelA in pancreatic tumor cells may reduce their invasive and metastatic potential.

A mouse chromosome 19 genetic map including the Lvis1 viral insertion site

Somatic insertion mutations, such as those caused by the insertion of a proviral element, can contribute to abnormal cell growth by activating cellular proto-oncogenes or inactivating tumor suppressor genes. Lvis1 is a genomic locus frequently disrupted by viral insertion in AKXD B-cell lymphomas (manuscript submitted for publication). To determine whether insertion mutations at Lvis1 affect a known proto-oncogene or tumor suppressor gene, we mapped Lvis1 to distal mouse chromosome 19. A detailed molecular genetic map of this region was constructed, localizing Lvis1 relative to 20 gene and microsatellite markers, 3 of which have not been mapped in the mouse (Nfkb2, Nlz, and Wnt8b). This analysis revealed that Lvis1 maps between two previously identified viral insertion sites, His2 and Frat1, and does not cosegregate with known gene markers. In addition, our study refines the gene order for distal mouse chromosome 19 and expands the comparative map between mouse chromosome 19 and the human chromosome 10q23-q26 homology region.

Rel transcription factors contribute to elevated urokinase expression in human ovarian carcinoma cells

Elevated levels of the urokinase-type plasminogen activator (uPA) in tumor cells are conductive to tumor cell spread and metastasis. In a previous study we observed that suppression of RelA dramatically reduced endogenous uPA synthesis in the human ovarian cancer cell line OV-MZ-6. Because the uPA promoter contains three potential Rel-like protein binding motifs (RRBE, 5'-NF-kappaB, and 3'-NF-kappaB) we conducted the first thorough systematic uPA promoter analysis to examine the direct impact of Rel proteins on uPA gene transcription. Disruption of RRBE resulted in a approximately 40% decrease in uPA promoter activity, mutation of the 5'-NF-kappaB motif led to an additional 20% decrease. The 3'-NF-kappaB motif was not active. Overexpression of RelA significantly enhanced uPA promoter activity, whereas IkappaB-alpha overexpression reduced uPA promoter activity by 40%. These data were supported by the finding that endogenous uPA was also increased sixfold by overexpression of RelA and decreased by 30% upon overexpression of IkappaB-alpha. Transfection of OV-MZ-6 cells with antisense deoxynucleotides directed to RelA expression reduced uPA promoter activity by at least 40%. Our data clearly suggest that by binding to uPA promoter elements, Rel transcripton factors contribute directly to elevated uPA gene expression in human ovarian cancer cells, thereby promoting the multiple functions of uPA during tumor growth and metastasis.

IkappaB kinase-alpha and -beta genes are coexpressed in adult and embryonic tissues but localized to different human chromosomes

Activation of the transcription factor nuclear factor kappa B (NF-kappaB) is regulated by phosphorylation, ubiquitination, and degradation of its inhibitory factor IkappaB. Very recently, two closely related serine/threonine kinases have been identified as IkappaB kinases which are essential for IkappaB phosphorylation and NF-kappaB activation. Here, we isolated the full-length human cDNA clones encoding these two IkappaB kinases, IKK-alpha and IKK-beta. Both polypeptides contain a conserved amino-terminal kinase domain, a leucine zipper motif and a helix-loop-helix domain at their carboxyl terminus. We showed that IKK-alpha and IKK-beta were coexpressed in most human adult tissues as well as in different developmental stages of mouse embryos, suggesting that they may cooperate in the cells. The IKK-alpha and IKK-beta genes are distinct but evolutionarily conserved. Moreover, the IKK-alpha gene locus was mapped to human chromosome 10q24, whereas the IKK-beta gene locus was localized to human chromosome 8p11.2. These results indicated that both genes are not clustered on the same chromosome; nevertheless, both genes may be still regulated similarly during development and in adult tissues.

NF-kappaB2 is a putative target gene of activated Notch-1 via RBP-Jkappa

NF-kappaB2 (p100/p52), a member of the NF-kappaB/Rel family of transcription factors, is involved in the regulation of a variety of genes important for immune function. Previously, we have shown that the NF-kappaB2 gene is regulated in a positive and a negative manner. Two kappaB elements within the NF-kappaB2 promoter mediate tumor necrosis factor alpha-inducible transactivation. In addition, we have shown that there exists a transcriptional repression in the absence of NF-kappaB. To identify a DNA binding activity responsible for this transcriptional repression, we have partially purified a nuclear complex, named Rep-kappaB. Here we further analyze this putative repressive binding activity. Detailed examination of Rep-kappaB-DNA interaction revealed the sequence requirements for binding to be almost identical to those of recombination signal binding protein Jkappa (RBP-Jkappa), the mammalian homolog of the protein encoded by Drosophila suppressor of hairless [Su(H)]. In addition, in electromobility shift assays, Rep-kappaB binding activity is recognized by an antibody directed against RBP-Jkappa. By performing transient-transfection assays, we show that human RBP-Jkappa represses basal as well as RelA (p65)-stimulated NF-kappaB2 promoter activity. Studies in Drosophila melanogaster have shown that Su(H) is implicated in the Notch signaling pathway regulating cell fate decisions. In transient-transfection assays we show that truncated Notch-1 strongly induces NF-kappaB2 promoter activity. In summary, our data clearly demonstrate that Rep-kappaB is closely related or identical to RBP-Jkappa. RBP-Jkappa is a strong transcriptional repressor of NF-kappaB2. Moreover, this repression can be overcome by activated Notch-1, suggesting that NF-kappaB2 is a novel putative Notch target gene.

Interaction between cell cycle regulator, E2F-1, and NF-kappaB mediates repression of HIV-1 gene transcription

The NF-kappaB/Rel family of transcription factors is one of the main targets of cytokines and other agents that induce HIV-1 gene expression. Some of these extracellular stimuli arrest cells in the G1 phase of the mitotic division cycle and modulate the activity of the tumor suppressor protein Rb and its partner E2F-1. Earlier studies indicated that E2F-1, a transcription factor that stimulates expression of S-phase-specific genes, is able to repress transcription directed by the human immunodeficiency virus (HIV-1) type-1 promoter in a variety of cells, including those of glial and lymphocytic origin. Here, we demonstrate that E2F-1 may regulate the activity of the HIV-1 long terminal repeat through its ability to bind sequences in the NF-kappaB enhancer region and to interact with the NF-kappaB subunit, p50. Gel retardation and methylation interference assays show that E2F-1 is able to bind specifically to a site embedded within the two NF-kappaB elements. Gel retardation/immunoblot analysis using purified E2F-1 and p50 homodimers reveals the presence of complexes containing both proteins. Affinity chromatography and co-immunoprecipitation assays provide evidence for direct interaction of E2F-1 and p50 in the absence of their DNA target sequences. In vitro transcription assay demonstrates that E2F-1 represses NF-kappaB mediated transcription in a cell-free system. Functional studies in Jurkat T lymphocytic cells point to the importance of both the E2F and NF-kappaB binding sites in E2F-1 mediated repression of HIV-1 promoter, in vivo. The results of this study suggest that NF-kappaB activity may be regulated by its interaction with the cell cycle regulatory protein, E2F-1.

Transcriptional regulation of NF-kappa B2: evidence for kappa B-mediated positive and negative autoregulation

NF-kappa B is an inducible transcription factor complex which regulates the expression of a variety of genes which are involved in the immune, inflammatory, and acute-phase responses. The maintenance of NF-kappa B activity in stimulated cells requires ongoing protein synthesis, suggesting several modes of regulation. In this report, we have characterized the transcriptional regulation of one family member, NF-kappa B2. The genomic structure and sequence of NF-kappa B2 revealed the presence of two promoters and at least four kappa B regulatory elements, which mediate responsiveness to phorbol myristate acetate and tumor necrosis factor alpha. Similar to other NF-kappa B family members, NF-kappa B2 is positively autoregulated. In contrast to other family members, we find that kappa B elements in the NFKB2 promoter can also mediate transcriptional repression in the absence of NF-kappa B. We identified a nuclear complex which binds specifically to a subset of kappa B-related sites but not to the canonical kappa B element. Because of its putative inhibitory or repressive effect, this binding activity has been termed Rep-kappa B. This mechanism of repressing basal NF-kappa B2 transcription in an inactivated state enables the cell to tightly control NF-kappa B2 activity. These data demonstrate that a novel mode of kappa B-dependent regulation is mediated by specific kappa B sites in the NFKB2 promoter.

Transcriptional regulation of NF-kappa B2: evidence for kappa B-mediated positive and negative autoregulation

NF-kappa B is an inducible transcription factor complex which regulates the expression of a variety of genes which are involved in the immune, inflammatory, and acute-phase responses. The maintenance of NF-kappa B activity in stimulated cells requires ongoing protein synthesis, suggesting several modes of regulation. In this report, we have characterized the transcriptional regulation of one family member, NF-kappa B2. The genomic structure and sequence of NF-kappa B2 revealed the presence of two promoters and at least four kappa B regulatory elements, which mediate responsiveness to phorbol myristate acetate and tumor necrosis factor alpha. Similar to other NF-kappa B family members, NF-kappa B2 is positively autoregulated. In contrast to other family members, we find that kappa B elements in the NFKB2 promoter can also mediate transcriptional repression in the absence of NF-kappa B. We identified a nuclear complex which binds specifically to a subset of kappa B-related sites but not to the canonical kappa B element. Because of its putative inhibitory or repressive effect, this binding activity has been termed Rep-kappa B. This mechanism of repressing basal NF-kappa B2 transcription in an inactivated state enables the cell to tightly control NF-kappa B2 activity. These data demonstrate that a novel mode of kappa B-dependent regulation is mediated by specific kappa B sites in the NFKB2 promoter.

Polymorphisms in the 3' untranslated region of the I kappa B/MAD-3 (NFKBI) gene located on chromosome 14

The NF-kappa B transcription factor regulates the expression of a number of genes, including immune function and growth control loci, and several viruses. For example, the long terminal repeat of the human immunodeficiency virus contains NF-kappa B binding sites. NF-kappa B activity in the nucleus is regulated by a cellular inhibitory protein I kappa B. To analyze the potential role of these genes in genetic disease we have mapped the NF-kappa B (NFKB2) and I kappa B/MAD-3 (NFKBI) loci in a panel of somatic cell hybrids to chromosomes 4 and 14, respectively. Amplification of the 3' untranslated region of NFKBI allows the detection of three independent polymorphisms within 410 bp. In combination these polymorphisms were informative in 27 of 36 CEPH families and allowed the gene to be placed onto the linkage map of chromosome 14, between the D14S32 and D14S42 markers.

The NF-kappa B transcription factor and cancer: high expression of NF-kappa B- and I kappa B-related proteins in tumor cell lines

NF-kappa B is a pleiotropic transcription factor which controls the expression of many genes and viruses. To date, there is good evidence, but no definitive proof, for its role in tumor formation and development of metastasis. To investigate the possibility that members of the NF-kappa B family could participate in the molecular control of the transformed and invasive phenotype, we examined the expression of these proteins in a variety of human tumor cell lines. The expression of p50, p65, p52 and I kappa B was quantified at the protein level using western immunoblot and mobility shift assay and at the RNA level by northern blot. We observed high expression of the NF-kappa B inhibitor I kappa B in the ovarian carcinoma cell line OVCAR-3 together with constitutive nuclear NF-kappa B activity. We also studied the colon carcinoma cell line HT-29 and its metastatic counterpart HTM-29 and we observed specific expression of the p52 NF-kappa B-related protein in the metastatic cells. Our data confirm that NF-kappa B could be involved in the genesis of a variety of cancers including solid tumors and provide us with interesting models to explore the exact role of these transcription factors in cancer.

Autosomal dominant polycystic kidney disease: localization of the second gene to chromosome 4q13-q23

At least two loci are known to exist for autosomal dominant polycystic kidney disease (ADPKD). One was localized to 16p, but the second less common locus has remained unlinked. Over 100 microsatellite markers, distributed across all chromosomes, have been typed on informative family members from the large Sicilian kindred in which the genetic heterogeneity was first discovered. Both the affected and the unaffected status of every family member used in the study were confirmed by renal ultrasonography. This search has resulted in the successful localization of a second ADPKD gene to chromosome 4q. It was found to be flanked by the markers D4S231 and D4S414, defining a segment that spans about 9 cM. The new locus has been designated PKD4. This second localization will allow researchers to target another ADPKD gene for isolation in an effort to understand the pathogenesis of this common disorder. Furthermore, when flanking markers for the second ADPKD gene are used in conjunction with flanking markers for PKD1, the accuracy of the diagnosis of the subtype of ADPKD present in any particular family will be enhanced. This will improve the accuracy of linkage-based presymptomatic diagnoses by reducing the error due to genetic heterogeneity.

NF-kappa B p100 (Lyt-10) is a component of H2TF1 and can function as an I kappa B-like molecule

NF-kappa B is an important transcription factor regulating expression of genes involved in immune function, inflammation, and cellular growth control. NF-kappa B activity is induced by numerous stimuli, such as phorbol esters, B- and T-cell mitogens, the cytokines tumor necrosis factor and interleukin-1, and serum growth factors. The standard model for the induction of NF-kappa B activity involves the release of the transcription factor from a cytoplasmic inhibitor termed I kappa B, allowing translocation of NF-kappa B to the nucleus. I kappa B contains multiple copies of the so-called ankyrin repeat, which are apparently necessary for its function. Subunits comprising NF-kappa B and related binding activities are members of the Rel multigene family. Two such subunits, p50 and p52 (also called p50B), are proteolytically processed from precursors of 105 kDa (also called p105 and NFKB1) and 100 kDa (also called p100, NFKB2, and Lyt-10), respectively. Both contain N-terminal Rel-homologous domains as well as multiple copies of C-terminal ankyrin repeats. We show here that NF-kappa B p100 is a component of the previously identified DNA-binding activity H2TF1. In addition, we show that p100 is localized in the cytoplasm in HeLa cells, where it is associated with c-Rel, p50, or p65 (RelA). In transient-transfection assays, p100 represses the ability of NF-kappa B p65 to activate a kappa B-containing reporter construct. Transfection of p100 also results in a loss of nuclear p65 DNA binding to a kappa B probe, as measured by an electrophoretic mobility shift assay, and a loss of nuclear p65 immunoreactivity, as measured by immunoblotting. This loss of nuclear p65 is paralleled by a gain of p65 DNA-binding activity and immunoreactivity in the cytoplasm. We interpret these data as demonstrating that p100 functions as an I kappa B-like molecule to sequester Rel family members in the cytoplasm. Proteolytic processing of p100 to the activator p52 is predicted to generate several new forms of Rel family heterodimers and therefore represents a form of regulation of NF-kappa B activity distinct from the classic I kappa B pathway.

NF-kappa B p100 (Lyt-10) is a component of H2TF1 and can function as an I kappa B-like molecule

NF-kappa B is an important transcription factor regulating expression of genes involved in immune function, inflammation, and cellular growth control. NF-kappa B activity is induced by numerous stimuli, such as phorbol esters, B- and T-cell mitogens, the cytokines tumor necrosis factor and interleukin-1, and serum growth factors. The standard model for the induction of NF-kappa B activity involves the release of the transcription factor from a cytoplasmic inhibitor termed I kappa B, allowing translocation of NF-kappa B to the nucleus. I kappa B contains multiple copies of the so-called ankyrin repeat, which are apparently necessary for its function. Subunits comprising NF-kappa B and related binding activities are members of the Rel multigene family. Two such subunits, p50 and p52 (also called p50B), are proteolytically processed from precursors of 105 kDa (also called p105 and NFKB1) and 100 kDa (also called p100, NFKB2, and Lyt-10), respectively. Both contain N-terminal Rel-homologous domains as well as multiple copies of C-terminal ankyrin repeats. We show here that NF-kappa B p100 is a component of the previously identified DNA-binding activity H2TF1. In addition, we show that p100 is localized in the cytoplasm in HeLa cells, where it is associated with c-Rel, p50, or p65 (RelA). In transient-transfection assays, p100 represses the ability of NF-kappa B p65 to activate a kappa B-containing reporter construct. Transfection of p100 also results in a loss of nuclear p65 DNA binding to a kappa B probe, as measured by an electrophoretic mobility shift assay, and a loss of nuclear p65 immunoreactivity, as measured by immunoblotting. This loss of nuclear p65 is paralleled by a gain of p65 DNA-binding activity and immunoreactivity in the cytoplasm. We interpret these data as demonstrating that p100 functions as an I kappa B-like molecule to sequester Rel family members in the cytoplasm. Proteolytic processing of p100 to the activator p52 is predicted to generate several new forms of Rel family heterodimers and therefore represents a form of regulation of NF-kappa B activity distinct from the classic I kappa B pathway.

Dimerization of NF-KB2 with RelA(p65) regulates DNA binding, transcriptional activation, and inhibition by an I kappa B-alpha (MAD-3)

Inducible expression of human immunodeficiency virus (HIV) is regulated by a cellular transcription factor, nuclear factor kappa B (NF-kappa B). NF-kappa B is composed of distinct subunits; five independent genes, NFKB1(p105), NFKB2(p100), RelA(p65), c-rel and relB, that encode related proteins that bind to kappa B DNA elements have been isolated. We have previously found that NFKB2(p49/p52) acts in concert with RelA(p65) to stimulate the HIV enhancer in Jurkat T-leukemia cells. Here we examine the biochemical basis for the transcriptional regulation of HIV by NFKB2. Using Scatchard analysis, we have determined the dissociation constants of homodimeric p49 and heterodimeric p49/p65 for binding to the HIV kappa B site. p49 has a approximately 18-fold-lower affinity for the HIV kappa B site (KD = 69.1 pM) than does the approximately 50-kDa protein NFKB1(p50) derived from p105 (KD = 3.9 pM). In contrast, the affinity of heterodimeric NFKB2(p49)/RelA(p65) for this site is approximately 6-fold higher (KD = 11.8 pM) than that of p49 alone. Consistent with these findings, in vitro transcription was stimulated 18-fold by the addition of preformed, heterodimeric NFKB2(p49)/RelA(p65) protein. Transcriptional activation of the HIV enhancer was also subject to regulation by recently cloned I kappa B-alpha(MAD-3). Recombinant I kappa B-alpha(MAD-3) inhibited the DNA binding activity of p65, p49/p65, and p50/p65 but stimulated the binding of NFKB2(p49) or NFKB1(p50). Functional activation of an HIV reporter plasmid by p49/p65 in transiently transfected Jurkat T-leukemia cells was also inhibited by coexpression of MAD-3. These data suggest that binding of the NFKB2 subunit to the HIV enhancer is facilitated by RelA(p65) and that this NFKB2(p49)/p65 heterodimeric complex mediates transcriptional activation which is subject to regulation by MAD-3.

Dimerization of NF-KB2 with RelA(p65) regulates DNA binding, transcriptional activation, and inhibition by an I kappa B-alpha (MAD-3)

Inducible expression of human immunodeficiency virus (HIV) is regulated by a cellular transcription factor, nuclear factor kappa B (NF-kappa B). NF-kappa B is composed of distinct subunits; five independent genes, NFKB1(p105), NFKB2(p100), RelA(p65), c-rel and relB, that encode related proteins that bind to kappa B DNA elements have been isolated. We have previously found that NFKB2(p49/p52) acts in concert with RelA(p65) to stimulate the HIV enhancer in Jurkat T-leukemia cells. Here we examine the biochemical basis for the transcriptional regulation of HIV by NFKB2. Using Scatchard analysis, we have determined the dissociation constants of homodimeric p49 and heterodimeric p49/p65 for binding to the HIV kappa B site. p49 has a approximately 18-fold-lower affinity for the HIV kappa B site (KD = 69.1 pM) than does the approximately 50-kDa protein NFKB1(p50) derived from p105 (KD = 3.9 pM). In contrast, the affinity of heterodimeric NFKB2(p49)/RelA(p65) for this site is approximately 6-fold higher (KD = 11.8 pM) than that of p49 alone. Consistent with these findings, in vitro transcription was stimulated 18-fold by the addition of preformed, heterodimeric NFKB2(p49)/RelA(p65) protein. Transcriptional activation of the HIV enhancer was also subject to regulation by recently cloned I kappa B-alpha(MAD-3). Recombinant I kappa B-alpha(MAD-3) inhibited the DNA binding activity of p65, p49/p65, and p50/p65 but stimulated the binding of NFKB2(p49) or NFKB1(p50). Functional activation of an HIV reporter plasmid by p49/p65 in transiently transfected Jurkat T-leukemia cells was also inhibited by coexpression of MAD-3. These data suggest that binding of the NFKB2 subunit to the HIV enhancer is facilitated by RelA(p65) and that this NFKB2(p49)/p65 heterodimeric complex mediates transcriptional activation which is subject to regulation by MAD-3.