Physical determinants of intermembrane protein transfer

Intermembrane protein transfer between erythrocytes and phospholipid vesicles was examined under a variety of conditions to investigate physical factors governing this process. Human erythrocytes were incubated with sonicated dimyristoylphosphatidylcholine vesicles containing trace [14C]dipalmitoylphosphatidylcholine. Protein-vesicle complexes were separated from cells and from membrane fragments by density gradient centrifugation. The yield of isolated protein vesicles was determined from the 14C-vesicle marker; protein compositions were analyzed by SDS-polyacrylamide gel electrophoresis. Enzymatic removal of portions of the cytoplasmic or exoplasmic domains of cell membrane proteins had little effect on the extent of protein transfer. Membrane additives such as cholate produced a 2-fold increase in protein-vesicle yield. The selectivity of protein transfer from erythrocytes was influenced by the lipid composition of recipient vesicles: inclusion of cholesterol increased band 3 content while the presence of anionic phospholipids reduced transfer. Proteins transferred from 32P-labeled cells differed in specific radioactivity from bulk cell proteins: glycophorin, highly phosphorylated in the cell membrane, showed no detectable labeling in the corresponding protein-vesicle band. These observations suggest that cell-to-vesicle protein transfer is insensitive to bulk steric and electrostatic properties of cell membranes, but enhanced by membrane defects. Recipient membrane composition influences the selectivity of transferred proteins and may reveal subtle differences in the membrane association of protein subpopulations.

Conformational changes of E. coli RNA polymerase during transcription initiation

Escherichia coli RNA polymerase-promoter complex undergoes a multistep process to initiate transcription. We have employed fluorescence spectroscopic approaches to detect the conformational states of the enzyme during this multistep process. A fluorescence assay based on the measurement of fluorescence of free and promoter-bound enzyme as a function of temperature within the range of 4 to 37 degrees C showed that, starting with initial 'closed complex', there are conformationally two distinct intermediate states of the polymerase till it attains the final form required for transcription initiation. The equilibrium from closed complex (RPc) to open complex (RPo) consists of at least the following two intermediate complexes: [formula: see text] Higher order structure of RNAP in each of these complexes was probed by means of measurement of accessibilities of the tryptophan fluorophores to the acrylamide. In the next part of the study, TbGTP, a fluorescent substrate, has been used to probe the state of active site in the enzyme for the complexes RPc, RPi1, RPi2 and RPo, respectively. From the comparison of changes in the parameters such as, fluorescence polarization anisotropy of TbGTP and its accessibility to the neutral quencher, acrylamide, in free and promoter-bound enzyme, we have further substantiated the first part of our results. Together these results suggest that formations of RPc and RPi1 do not involve radical conformational changes in the enzyme, while the enzyme undergoes major change in conformation in the steps RPil-->RPi2 and RPi2-->RPo. The strong tryptophan promoter cloned in plasmid pDR720 was chosen as a model promoter in these studies.

Phase contrast microscopic evaluation of placental pathology in premature gestation

Numerous representative samples taken from forty placentas immediately after delivery from mothers associated with prematurity (i.e. less than 38 weeks), were semiquantitatively studied by phase contrast microscopy. Twenty placentas delivered from mothers without any antenatal complication served as control. Hypoplasia of the syncytium, stromal edema, ischaemia were prominent findings on phase contrast microscopy in the study group. Increased basement membrane thickening and high villous edema scores observed on light microscopy were statistically significant in prematurity as compared to controls. Observations by phase contrast and light microscopy were found complementary to each other. Phase contrast microscopy provided quicker results without disadvantage of fixation artefact and was found distinctly superior over the conventional histological methods.

Activation of IL-2 receptor alpha-chain gene by individual members of the rel oncogene family in association with serum response factor

Expression of the IL-2R alpha gene is regulated by members of the c-Rel/NF-kappa B family of transcription factors binding to the kappa B site in the promoter. Previous work has not defined the role of individual members of the c-Rel family in the activation of the IL-2R alpha gene. Using the COS cell system, we were able to reconstitute the regulation of the IL-2R alpha promoter by expressing cloned Rel family members with serum response factor (SRF). We found that c-rel alone activated the IL-2R alpha promoter only weakly but worked with the p50 subunit of NF-kappa B (NFKB1) to give a higher level of expression. We showed that c-rel heterodimerizes with p50 and the amount of this heterodimer correlated with the level of IL-2R alpha gene expression. Our results provide evidence that c-rel/p50 heterodimers activate gene expression in the context of a cellular promoter. We show that c-rel or p65 can cooperate with SRF in the activation of this promoter and the transactivation by c-rel with SRF was enhanced by p50. Synergistic activation required both kappa B and CArG sites, and binding studies show that these adjacent sites can be occupied simultaneously. The transactivation observed with cloned transcription factors mimics the physiologic induction of the IL-2R alpha gene since multiple sequence elements cooperate to give gene activation. The data support the model that c-rel/p50 or p65 can cooperate with SRF to specifically target the expression of the IL-2R alpha gene in activated T cells.

Activation of IL-2 receptor alpha-chain gene by individual members of the rel oncogene family in association with serum response factor

Expression of the IL-2R alpha gene is regulated by members of the c-Rel/NF-kappa B family of transcription factors binding to the kappa B site in the promoter. Previous work has not defined the role of individual members of the c-Rel family in the activation of the IL-2R alpha gene. Using the COS cell system, we were able to reconstitute the regulation of the IL-2R alpha promoter by expressing cloned Rel family members with serum response factor (SRF). We found that c-rel alone activated the IL-2R alpha promoter only weakly but worked with the p50 subunit of NF-kappa B (NFKB1) to give a higher level of expression. We showed that c-rel heterodimerizes with p50 and the amount of this heterodimer correlated with the level of IL-2R alpha gene expression. Our results provide evidence that c-rel/p50 heterodimers activate gene expression in the context of a cellular promoter. We show that c-rel or p65 can cooperate with SRF in the activation of this promoter and the transactivation by c-rel with SRF was enhanced by p50. Synergistic activation required both kappa B and CArG sites, and binding studies show that these adjacent sites can be occupied simultaneously. The transactivation observed with cloned transcription factors mimics the physiologic induction of the IL-2R alpha gene since multiple sequence elements cooperate to give gene activation. The data support the model that c-rel/p50 or p65 can cooperate with SRF to specifically target the expression of the IL-2R alpha gene in activated T cells.

Expression and induction of nuclear factor-kappa B-related proteins in thymocytes

Thymocytes mature in response to the cues from the thymic micro-environment, which regulate stage-specific gene expression during development. We find that several proteins that bind the kappa B sequence in vitro are constitutively activated in freshly isolated thymocytes. These include the rel-related p50 homodimers, p50/p65 heterodimers, low levels of c-rel, and two other factors that may be thymus specific. Disruption of the thymic micro-environment resulted in loss of DNA-binding, suggesting that lymphocyte-stromal cell interactions induce and maintain these proteins in a DNA-binding form. Phorbol ester and ionomycin treatment induced p50, p65, and p68 c-rel kappa B DNA-binding activity. Expression of p68 c-rel protein, but not p50 or p65, was suppressed by the immunosuppressive drug FK506. Because FK506 specifically inhibits the appearance of mature single-positive thymocytes, gene expression regulated by p68 c-rel may play a role in selection and maturational signals involved in the double-positive to single-positive transition.

Expression and induction of nuclear factor-kappa B-related proteins in thymocytes

Thymocytes mature in response to the cues from the thymic micro-environment, which regulate stage-specific gene expression during development. We find that several proteins that bind the kappa B sequence in vitro are constitutively activated in freshly isolated thymocytes. These include the rel-related p50 homodimers, p50/p65 heterodimers, low levels of c-rel, and two other factors that may be thymus specific. Disruption of the thymic micro-environment resulted in loss of DNA-binding, suggesting that lymphocyte-stromal cell interactions induce and maintain these proteins in a DNA-binding form. Phorbol ester and ionomycin treatment induced p50, p65, and p68 c-rel kappa B DNA-binding activity. Expression of p68 c-rel protein, but not p50 or p65, was suppressed by the immunosuppressive drug FK506. Because FK506 specifically inhibits the appearance of mature single-positive thymocytes, gene expression regulated by p68 c-rel may play a role in selection and maturational signals involved in the double-positive to single-positive transition.

FK506 inhibits antigen receptor-mediated induction of c-rel in B and T lymphoid cells

Stimulation of B and T cells via the antigen receptor, by phorbol ester or by phorbol ester and ionomycin, leads to nuclear translocation of the inducible transcription factor NF-kappa B, comprising the p50 and p65 rel-related polypeptides. In this report we show that c-rel is a component of the antigen receptor-induced kappa B binding proteins in both B and T cells. Whereas NF-kappa B can be induced by phorbol ester alone, optimal induction of c-rel requires stimulation by both phorbol ester and ionomycin, the dual signal that is necessary for proliferation of untransformed lymphocytes. Furthermore, c-rel induction is blocked by the immunosuppressive drug FK506 that is known to inhibit B and T cell activation. c-rel-dependent transactivation of the interleukin-2 receptor alpha chain (IL-2R alpha) promoter is augmented by coexpression of calcineurin, suggesting the involvement of a calcineurin-dependent intracellular pathway. Our results identify c-rel as a target of immunosuppressive agents and illustrate the similarity of activation pathways in both B and T cells.

Induction of the transcription factors NF-kappa B, AP-1 and NF-AT during B cell stimulation through the CD40 receptor

To address elements that might uniquely characterize CD40 mediated signaling, the nuclear expression of three transcription factors was evaluated following B cell stimulation by CD40L and by anti-Ig antibody. Cross-linked CD40L was found to induce nuclear expression of NF-kappa B, AP-1 and NF-AT with a time course and intensity similar to that produced by anti-Ig. Examination of NF-kappa B in more detail demonstrated that the CD40 mediated expression of DNA binding complexes correlated with induction of trans-activating activity which again attained similar levels following cross-linking of CD40 and slg. Despite the marked similarity in transcription factor induction triggered through CD40 and slg, differences in the intracellular signaling pathways utilized were apparent in that protein kinase C (PKC) depletion did not affect CD40 mediated induction of NF-kappa B even as induction by anti-Ig was abolished. These results suggest that a 'final common pathway' or convergence of transcription factor induction may exist for two distinct receptors, each of which is individually capable of triggering cell cycle progression, despite the use of separate intracellular signaling pathways that differ at the level of PKC. Although transcription factor induction was similar for CD40L and anti-Ig early on, subtle differences in expressed NF-kappa B and AP-1 nucleoprotein complexes were apparent at 24 h. Such differences may play a role in determining the variant effects on B cells of stimulation through these two receptors.

Nuclear factors that mediate intrathymic signals are developmentally regulated

Thymocytes mature through several stages of development, defined by cell surface markers such as CD3, CD4, and CD8, in response to environmental cues. Signal transduction resulting from lymphocyte-stromal cell interactions is likely to activate inducible transcription factors which in turn govern stage-specific gene expression. In this report we show that inducible transcription factors such as AP-1 and NF-AT are constitutively nuclear, in response to intrathymic signals, in freshly isolated thymocytes at all stages of maturation. In CD4+CD8+ double positive (DP), but not in the more immature CD4-CD8- double negative (DN) thymocytes, constant stimulus from the thymic environment is required to maintain nuclear AP-1. Thus, disruption of the thymus and incubation of thymocytes at 37 degrees C downregulates DNA binding by nuclear factors AP-1 and NF-AT. Similar treatment of thymocytes has previously been shown to downregulate CD3 zeta chain phosphorylation and increase T cell receptor CD3 expression on DP thymocytes, which is a feature of repertoire selection. Since mature T cells maintain inducible nuclear factors in an inactive form until an encounter with antigen, we propose that downregulation of nuclear DNA binding proteins may reflect another feature of this stage of T cell maturation.

PU.1 and an HLH family member contribute to the myeloid-specific transcription of the Fc gamma RIIIA promoter

Expression of the low-affinity Fc receptor for IgG (murine Fc gamma RIIIA) is restricted to cells of myelomonocytic origin. We report here the promoter structure, the proximal DNA sequences responsible for transcription of Fc gamma RIIIA in macrophages and the protein factors which interact with these sequences. A 51 bp sequence, termed the myeloid restricted region (MRR), was both necessary and sufficient for conferring cell type-specific expression in macrophages. Reporter constructs containing mutations in this sequence result in the loss of MRR activity upon transfection into the macrophage cell line, RAW264.7. Two cis-acting elements have been identified and are required for full promoter function. These same elements analyzed by EMSA define two binding sites recognized by nuclear factors derived from macrophages. A 3' purine tract (-50 to -39) within the MRR binds the macrophage and B cell-specific factor, PU.1, and a second E box-like element, termed MyE, upstream of the PU.1 box (-88 to -78) binds the HLH factors TFE3 and USF. EMSA studies using RAW cell extracts suggest that both PU.1 and MyE factors may bind simultaneously to the MRR resulting in a ternary complex that is responsible, in part, for the myeloid-specific activity of the Fc gamma RIIIA promoter.

Intrinsic fluorescence of E. coli RNA polymerase as a probe for its conformational changes during transcription initiation

A simple fluorimetric assay based on internal fluorescence of tryptophan residues of E. Coli RNA polymerase has been developed to ascertain the number of steps during conversion of closed complex of the polymerase-promoter (trp promoter cloned in plasmid pDR720) to open complex. Our results from measurement on relative ratio of fluorescence at 340 nm (lambda ex = 295 nm) for free and promoter-bound RNA polymerase as a function of temperature, within the range 4 degrees C to 37 degrees C, indicate following equilibria for the above conversion: R+P<-->RPc<-->RPi1<-->RPi2<-->RPo. Apart from detection of one more intermediate in terms of conformational states of the bound RNA polymerase, second feature of our studies is the examination of conformational state of the polymerase using accessibility of fluorophor, tryptophan residues, to a neutral quencher, acrylamide, as the probe. We observe that in terms of accessibility of tryptophan residues in protein, intermediate complex, RPi2, is conformationally most perturbed in comparison to free polymerase. Implications of these results are discussed and compared with the available reports from footprinting and gel retardation assays of RNA polymerase-promoter interactions.

Cyclosporin A sensitivity of the NF-kappa B site of the IL2R alpha promoter in untransformed murine T cells

We have investigated the characteristics of IL2R alpha gene induction in untransformed murine T cells. Induction of IL2R alpha mRNA by TCR/CD3 ligands in a murine T cell clone and in short-term splenic T cell cultures was inhibited by protein synthesis inhibitors and by CsA. This result was contrary to previous observations in JURKAT T leukemia cells and human peripheral blood T cells, suggesting a difference in the mechanisms of IL2R alpha gene induction in these different cell types. The CsA sensitivity of IL2R alpha mRNA induction represented a direct effect on the TCR/CD3 response, and was not due to CsA-sensitive release of the lymphokines IL2 or tumour necrosis factor alpha (TNF alpha) and consequent lymphokine-mediated induction of IL2R alpha mRNA. The NF-kappa B site of the IL2R alpha promoter was essential for gene induction through the TCR/CD3 complex, and the induction of reporter plasmids containing multimers of this site was significantly inhibited by CsA. Northern blotting analysis indicated that while the p65 subunit of NF-kappa B was constitutively expressed and not appreciably induced upon T cell activation, mRNA for the p105 precursor of p50 NF-kappa B was induced in response to TCR/CD3 stimulation and this induction was sensitive to CsA. Electrophoretic mobility shift assays and antiserum against the p50 subunit of NF-kappa B indicated that p50 was a component of the inducible nuclear complex that bound to the IL2R alpha kappa B site. Appearance of the kB-binding proteins was insensitive to CsA at early times after activation (approximately 15 min), but was partially sensitive to CsA at later times. Based on these results, we propose that the NF-kappa B site of the IL2R alpha promoter mediates at least part of the CsA sensitivity of IL2R alpha gene induction in untransformed T cells, possibly because de novo synthesis of p105 NF-kappa B is required for sustained IL2R alpha expression.

Cyclosporin-A sensitive induction of NF-AT in murine B cells

Primary B cells are induced to proliferate by cross-linking surface immunoglobulin or by its pharmacological equivalent, phorbol ester and calcium ionophore. However, nuclear responses that have been studied in activated B cells are typically inducible with phorbol esters alone. We show that a factor, indistinguishable from the nuclear factor of activated T cells (NF-AT), is induced in B cells in response to anti-immunoglobulin signals or the combined action of phorbol ester and ionomycin, but not in response to either reagent alone. The signals necessary for NF-AT induction in B cells, therefore, closely parallel those required to induce B cell proliferation. Transfection analysis shows that B cell NF-AT is a transcriptional activator. Furthermore, NF-AT induction in splenic cells is suppressed by cyclosporin A, suggesting a mechanism by which immunosuppressive agents act on the B cell compartment. We propose that NF-AT should be considered more generally as a nuclear factor of activated lymphoid cells.

Clinico-haematological profile in acute and chronic Plasmodium falciparum malaria in children

The clinicohaematological findings of acute state (Group A, 30 patients) and chronic state (Group B, 34 patients) of falciparum malaria in paediatric patients are compared. The children with chronic falciparum malaria were apyrexic and presented with features of moderate to severe anaemia with hepato-splenomegaly. Greater severity of anaemia and haemolysis, higher incidence and severity of neutropenia, atypical lymphocytosis, monocytosis and thrombocytopenia were observed in patients with chronic falciparum malaria as compared to patients with acute falciparum malaria despite lesser degree of parasitaemia in the former as compared to the latter. While mechanical destruction of parasitised RBC's, ineffective and dysplastic erythropoiesis either due to unmasking of border line dierty folic acid deficiency or otherwise, transient hypoplasia of bone marrow, impaired utilization of iron and immune destruction of RBCs with hypersplenism may be the mechanisms for anaemia, transient hypoplasia of bone marrow and hypersplenism may be the factors responsible for thrombocytopenia and neutropenia.

Comparative evaluation of commonly used catheters through histopathological changes induced in bladder urothelium

There is growing concern about the toxic potential of chemicals coating various catheter materials, especially due to lack of international standards for toxicity testing. The present study evaluates the toxicity potential in terms of pathological changes induced by the catheters commonly used in practice, i.e. latex-, silicone- and Teflon-coated catheters. Teflon-coated catheters appear to be superior to others in the present study.

The bangladesh cyclone of 1991: why so many people died

Living with natural disasters has become a way of life in Bangladesh. On the night of 29 April 1991 a severe cyclonic storm, accompanied by tidal surges up to 30 feet high, battered the coastal areas of Bangladesh for 3-4 hours. Thousands of people were killed and property worth billions of dollars was destroyed. After the cyclone, several studies, using epidemiological and anthropological methods, looked at the impact of the cyclone. It was estimated that over 67,000 people lost their lives. Women, children and the elderly were much more at risk and so were those from the socio-economically disadvantaged section of the population. Cyclone shelters were few in relation to need but proved very helpful in saving lives. At least 20 per cent more deaths would have occurred in the absence of these shelters. The article documents impressive improvements in Bangladesh's-ability to cope and makes recommendations for the future.

Switch recombination breakpoints occur at nonrandom positions in the S gamma tandem repeat

Ig switch (S) recombination is clearly focused on S regions. It is possible that S-specific DNA binding proteins facilitate the alignment of these regions before recombination. The S gamma 3-specific DNA binding proteins, SNAP and SNIP/NF-kappa B, interact with two discrete regions of the S gamma 3 tandem repeat, the A and B sites. Recombination breakpoints in the S gamma 3 region were found to significantly correlate with the binding sites of the S gamma 3 binding proteins. We now report the conservation of the SNIP and SNAP binding sites in S gamma 2b and S gamma 1 DNA. SNIP/NF-kappa B interacts with its cognate sites in S gamma 2b and S gamma 1 DNA as determined by mobility shift assays, competition binding studies, and supershift analysis using an antiserum specific for the p50 component. SNAP binds specifically to S gamma 2b and S gamma 1 as measured by mobility shift assays and competition binding studies. SNAP is composed of two closely traveling mobilities that do not separate on partial purification. SNIP and SNAP are expressed in nuclear extracts derived from murine splenic B cell cultures stimulated with mitogen or mitogen and IL-4. No new DNA binding proteins specific for S gamma 1 tandem repeats are detectable in nuclear extracts from B cells stimulated with mitogen and IL-4. The sites at which recombination occurs in the S gamma 2b and S gamma 1 regions have been analyzed statistically and found to correlate with the SNIP/NF-kappa B and SNAP binding sites. Distinctions have been found regarding the use of DNA substrates within the tandem repeat between primary (mu-->gamma) and successive (gamma-->x) S recombination.

Switch recombination breakpoints occur at nonrandom positions in the S gamma tandem repeat

Ig switch (S) recombination is clearly focused on S regions. It is possible that S-specific DNA binding proteins facilitate the alignment of these regions before recombination. The S gamma 3-specific DNA binding proteins, SNAP and SNIP/NF-kappa B, interact with two discrete regions of the S gamma 3 tandem repeat, the A and B sites. Recombination breakpoints in the S gamma 3 region were found to significantly correlate with the binding sites of the S gamma 3 binding proteins. We now report the conservation of the SNIP and SNAP binding sites in S gamma 2b and S gamma 1 DNA. SNIP/NF-kappa B interacts with its cognate sites in S gamma 2b and S gamma 1 DNA as determined by mobility shift assays, competition binding studies, and supershift analysis using an antiserum specific for the p50 component. SNAP binds specifically to S gamma 2b and S gamma 1 as measured by mobility shift assays and competition binding studies. SNAP is composed of two closely traveling mobilities that do not separate on partial purification. SNIP and SNAP are expressed in nuclear extracts derived from murine splenic B cell cultures stimulated with mitogen or mitogen and IL-4. No new DNA binding proteins specific for S gamma 1 tandem repeats are detectable in nuclear extracts from B cells stimulated with mitogen and IL-4. The sites at which recombination occurs in the S gamma 2b and S gamma 1 regions have been analyzed statistically and found to correlate with the SNIP/NF-kappa B and SNAP binding sites. Distinctions have been found regarding the use of DNA substrates within the tandem repeat between primary (mu--&gt;gamma) and successive (gamma--&gt;x) S recombination.

Interaction of ribonucleotides with T7 RNA polymerase: probable role of GTP in transcription initiation

Interaction of ribonucleotides (NTP where N = G, A, C or U) with bacteriophage T7 RNA polymerase (T7 RNAP) was studied by fluorescence emission spectroscopy of the enzyme. From the NTP-concentration-dependent quenching of fluorescence of the enzyme, apparent dissociation constants for NTP-T7 RNAP was found to be in following order: UTP>CTP>>ATP>GTP. Acrylamide quenching of tryptophan fluorescence of free and bound enzyme suggests a conformational change, particularly in the case of GTP (and ATP). This is the first report of high affinity binding of the enzyme with purine ribonucleotides in the absence of promoter. These results also suggest that GTP may induce a promoter-specific conformation of the enzyme. The observation could account for specific requirement of GTP in transcription initiation reported earlier (1-4).

Functional GATA-3 binding sites within murine CD8 alpha upstream regulatory sequences

Genes encoding the accessory molecules CD8 and CD4 are activated early in thymocyte development, generating CD4+8+ double positive intermediates, which give rise to two functionally distinct mature T cell subsets that express either CD4 or CD8. The mechanisms that govern the activation or suppression of the CD8 gene are likely to be central to the T cell development program. To identify the key regulatory factors, we have initiated an analysis of the transcriptional regulation of the murine CD8 alpha gene. We have identified three CD8+ cell-specific DNAase I hypersensitive sites (HSS) located upstream of the murine CD8 alpha gene. In vitro mobility shift analysis of the -4.0-kb HSS region has revealed multiple binding sites for the T cell-restricted transcription factor GATA-3. In vitro translated murine GATA-3 binds specifically to both CD8 GATA sites, and coexpression of this factor in transient transfection assays transactivates a reporter construct containing these sequences. These results provide the first evidence for the role of a T cell-restricted factor in the regulation of either CD8 or CD4 genes.

Regulation of lymphoid-specific immunoglobulin mu heavy chain gene enhancer by ETS-domain proteins

The enhancer for the immunoglobulin mu heavy chain gene (IgH) activates a heterologous gene at the pre-B cell stage of B lymphocyte differentiation. A lymphoid-specific element, microB, is necessary for enhancer function in pre-B cells. A microB binding protein is encoded by the PU.1/Spi-1 proto-oncogene. Another sequence element, microA, was identified in the mu enhancer that binds the product of the ets-1 proto-oncogene. The microA motif was required for microB-dependent enhancer activity, which suggests that a minimal B cell-specific enhancer is composed of both the PU.1 and Ets-1 binding sites. Co-expression of both PU.1 and Ets-1 in nonlymphoid cells trans-activated reporter plasmids that contained the minimal mu enhancer. These results implicate two members of the Ets family in the activation of IgH gene expression.

Abnormal kappa B-binding protein in the cytoplasm of a plasmacytoma cell line that lacks nuclear expression of NF-kappa B

The transcription factor NF-kappa B appears to play an important role in immunoglobulin gene expression and lymphokine production, and may play a role in primary B cell activation. Constitutive nuclear expression of NF-kappa B has been found in all mature B cell lines with the notable exception of the murine plasmacytoma, S107. We report herein that S107 cells express cytoplasmic kappa B-binding material detected by electrophoretic mobility shift assay that by several criteria represents authentic NF-kappa B. Despite the presence of cytoplasmic NF-kappa B, several stimuli known to induce nuclear translocation of NF-kappa B failed to do so in S107 cells, including: the PKC agonist, PMA; the protein synthesis inhibitor, cycloheximide; and LPS. Transfection of S107 cells with a kappa B-CAT reporter gene construct confirmed the absence of functional activity. Importantly, a global failure of nuclear transcription factor expression was ruled out by the ability of PMA to induce nuclear expression of another trans-acting factor, AP-1. Thus, rather than lacking NF-kappa B altogether, S107 cells manifest disordered regulation of NF-kappa B in which cytoplasmic material is incapable of translocation to the nucleus. While Northern analysis failed to reveal a gross defect in the mRNA coding for the DNA binding subunit of NF-kappa B, UV-photo-cross-linking followed by denaturing gel electrophoresis demonstrated the presence of a cytoplasmic kappa B-binding protein of abnormally elevated molecular size. This finding suggests that the abnormal regulation of NF-kappa B in S107 cells is associated with the appearance of an unusual kappa B-binding molecule.