LTßR signalling preferentially accelerates oncogenic AKT-initiated liver tumours.

OBJECTIVES: The relative contributions of inflammatory signalling and sequential oncogenic dysregulation driving liver cancer pathogenesis remain incompletely understood. Lymphotoxin-ß receptor (LTßR) signalling is critically involved in hepatitis and liver tumorigenesis. Therefore, we explored the interdependence of inflammatory lymphotoxin signalling and specific oncogenic pathways in the progression of hepatic cancer. DESIGN: Pathologically distinct liver tumours were initiated by hydrodynamic transfection of oncogenic V-Akt Murine Thymoma Viral Oncogene Homolog 1 (AKT)/ß-catenin or AKT/Notch expressing plasmids. To investigate the relationship of LTßR signalling and specific oncogenic pathways, LTßR antagonist (LTßR-Fc) or agonist (anti-LTßR) were administered post oncogene transfection. Initiated livers/tumours were investigated for changes in oncogene expression, tumour proliferation, progression, latency and pathology. Moreover, specific LTßR-mediated molecular events were investigated in human liver cancer cell lines and through transcriptional analyses of samples from patients with intrahepatic cholangiocarcinoma (ICC). RESULTS: AKT/ß-catenin-transfected livers displayed increased expression of LTß and LTßR, with antagonism of LTßR signalling reducing tumour progression and enhancing survival. Conversely, enforced LTßR-activation of AKT/ß-catenin-initiated tumours induced robust increases in proliferation and progression of hepatic tumour phenotypes in an AKT-dependent manner. LTßR-activation also rapidly accelerated ICC progression initiated by AKT/Notch, but not Notch alone. Moreover, LTßR-accelerated development coincides with increases of Notch, Hes1, c-MYC, pAKT and ß-catenin. We further demonstrate LTßR signalling in human liver cancer cell lines to be a regulator of Notch, pAKTser473 and ß-catenin. Transcriptome analysis of samples from patients with ICC links increased LTßR network expression with poor patient survival, increased Notch1 expression and Notch and AKT/PI3K signalling. CONCLUSIONS: Our findings link LTßR and oncogenic AKT signalling in the development of ICC.

Architecture of high-affinity unnatural-base DNA aptamers toward pharmaceutical applications.

We present a remodeling method for high-affinity unnatural-base DNA aptamers to augment their thermal stability and nuclease resistance, for use as drug candidates targeting specific proteins. Introducing a unique mini-hairpin DNA provides robust stability to unnatural-base DNA aptamers generated by SELEX using genetic alphabet expansion, without reducing their high affinity. By this method, >80% of the remodeled DNA aptamer targeting interferon-γ (KD of 33 pM) survived in human serum at 37 °C after 3 days under our experimental conditions, and sustainably inhibited the biological activity of interferon-γ.

Pattern and predictors of immunologic recovery in HIV infected patients.

BACKGROUND: Although anti-retroviral therapy has generally improved the survival of HIV infected patients in many developing countries including Ghana, specific socio-demographic factors could still influence outcome of treatment. This study was designed to identify patient-specific factors that could influence the immune recovery of absolute CD4 count in HIV infected patients. FINDINGS: Hospital records were extracted from two health facilities in Ghana. The impact of socio-demographic factors type of ART and baseline category of CD4 counts were assessed at six monthly interval using robust linear mixed models. RESULTS: A total of 214 follow up records were reviewed at Komfo Anokye Teaching Hospital (KATH) and the Kumasi South Hospital (KSH). One hundred (46.7%) were from KATH and 114 (53.3%) were from KSH. There was a general increase in the level of CD4 counts with time, however this increase significantly slowed down with subsequent reviews (p < 0.001). On the average the rate of CD4 count recovery slowed down by 43.6 cells/µl for every 6 months of follow up (SE = 7.69; p < 0.001). Similarly the recovery of CD4 counts in subjects with an initial high baseline CD4 counts decreased by 192.6 cells/µl (SD error = 42.3, p value ≤0.001). All other variables were not significantly associated with recovery of CD4 counts. CONCLUSION: Our study has demonstrated the well-known phenomenon of CD4 counts increasing after administration of ARTs. CD4 counts increased more rapidly in those with relatively lower initial counts, catching up with those with high CD4 count by 2 years post treatment.

Mechanism of action for the cytotoxic effects of the nitric oxide prodrug JS-K in murine erythroleukemia cells.

The nitric oxide (NO) prodrug JS-K, a promising anti-cancer agent, consists of a diazeniumdiolate group necessary for the release of NO as well as an arylating ring. In this study, we research the mechanism by which JS-K kills a murine erythroleukemia cell line and determine the roles of NO and arylation in the process. Our studies indicate that JS-K inhibits the PI 3-kinase/Akt and MAP kinase pathways. This correlates with the activation of the tumor suppressor FoxO3a and increased expression of various caspases, leading to apoptosis. The arylating capability of JS-K appears to be sufficient for inducing these biological effects. Overall, these data suggest that JS-K kills tumor cells by arylating and inactivating signaling molecules that block the activation of a tumor suppressor.

Role of N-terminal sequences of the tyrosine kinase sf-Stk in transformation of rodent fibroblasts by variants of Friend spleen focus-forming virus.

Infection of erythroid cells by Friend spleen focus-forming virus (SFFV) leads to acute erythroid hyperplasia in mice, due to expression of its unique envelope glycoprotein, gp55. Erythroid cells expressing SFFV gp55 proliferate in the absence of their normal regulator, erythropoietin, because of the interaction among the viral envelope protein, the erythropoietin receptor, and a short form of the receptor tyrosine kinase Stk (sf-Stk). This leads to constitutive activation of several signal transduction pathways. Our previous studies showed that sf-Stk interacts with SFFV gp55, forming disulfide-linked complexes. This covalent interaction, along with other noncovalent interactions with SFFV-gp55, results in constitutive tyrosine phosphorylation of sf-Stk and rodent fibroblast transformation. Here, we determined the precise amino acid region within sf-Stk that contributes to fibroblast transformation by the polycythemia-inducing (SFFV-P) and the anemia-inducing (SFFV-A) strains of SFFV. Sf-Stk deletion mutants showed different transforming abilities in fibroblasts infected with SFFV-P and SFFV-A, although the N-terminal extracellular domain of sf-Stk was essential for fibroblast transformation by both viruses. Point mutations of sf-Stk indicated that cysteine 19 was critical for fibroblast transformation by SFFV-P, although all four cysteines (8, 19, 37 and 42) appeared to be important for fibroblast transformation by both SFFV-P and SFFV-A. Mutation of sf-Stk cysteine 19 abolished its ability to form dimers with SFFV-P and SFFV-A gp55. These results suggest that the interaction between sf-Stk and the envelope proteins of the polycythemia- and anemia-inducing variants of SFFV is architecturally different.

Retrovirus-transformed erythroleukemia cells induce central nervous system failure in a new syngeneic mouse model of meningeal leukemia.

Lack of suitable mouse models for central nervous system (CNS)-associated leukemias has hindered mechanism-guided development of therapeutics. By transplanting retrovirus-transformed mouse erythroleukemia cells into syngeneic mice, we developed a new animal model of meningeal leukemia associated with rapid paralysis. Necropsy revealed massive proliferation of the leukemic cells in the bone marrow (BM) followed by pathological angiogenesis and invasion of the leukemic cells into the meninges of the CNS. Further analysis demonstrated that the erythroleukemia cells secreted high levels of VEGF and preferentially adhered in vitro to fibronectin. This unique animal model for meningeal leukemia should facilitate studies of engraftment and proliferation of leukemic cells in the BM and their invasion of the CNS as well as pre-clinical evaluation of experimental therapeutics for CNS-associated leukemias.

The human lung adenocarcinoma cell line EKVX produces an infectious xenotropic murine leukemia virus.

The cell lines of the NCI-60 panel represent different cancer types and have been widely utilized for drug screening and molecular target identification. Screening these cell lines for envelope proteins or gene sequences related to xenotropic murine leukemia viruses (X-MLVs) revealed that one cell line, EKVX, was a candidate for production of an infectious gammaretrovirus. The presence of a retrovirus infectious to human cells was confirmed by the cell-free transmission of infection to the human prostate cancer cell line LNCaP. Amplification and sequencing of additional proviral sequences from EKVX confirmed a high degree of similarity to X-MLV. The cell line EKVX was established following passage of the original tumor cells through nude mice, providing a possible source of the X-MLV found in the EKVX cells.

Role of phosphatidylinositol 3-kinase in friend spleen focus-forming virus-induced erythroid disease.

Infection of erythroid cells by Friend spleen focus-forming virus (SFFV) leads to acute erythroid hyperplasia in mice due to expression of its unique envelope glycoprotein, gp55. Erythroid cells expressing SFFV gp55 proliferate in the absence of their normal regulator, erythropoietin (Epo), because of interaction of the viral envelope protein with the erythropoietin receptor and a short form of the receptor tyrosine kinase Stk (sf-Stk), leading to constitutive activation of several signal transduction pathways. Our previous in vitro studies showed that phosphatidylinositol 3-kinase (PI3-kinase) is activated in SFFV-infected cells and is important in mediating the biological effects of the virus. To determine the role of PI3-kinase in SFFV-induced disease, mice deficient in the p85alpha regulatory subunit of class IA PI3-kinase were inoculated with different strains of SFFV. We observed that p85alpha status determined the extent of erythroid hyperplasia induced by the sf-Stk-dependent viruses SFFV-P (polycythemia-inducing strain of SFFV) and SFFV-A (anemia-inducing strain of SFFV) but not by the sf-Stk-independent SFFV variant BB6. Our data also indicate that p85alpha status determines the response of mice to stress erythropoiesis, consistent with a previous report showing that SFFV uses a stress erythropoiesis pathway to induce erythroleukemia. We further showed that sf-Stk interacts with p85alpha and that this interaction depends upon sf-Stk kinase activity and tyrosine 436 in the multifunctional docking site. Pharmacological inhibition of PI3-kinase blocked proliferation of primary erythroleukemia cells from SFFV-infected mice and the erythroleukemia cell lines derived from them. These results indicate that p85alpha may regulate sf-Stk-dependent erythroid proliferation induced by SFFV as well as stress-induced erythroid hyperplasia.

Neurodegeneration induced by PVC-211 murine leukemia virus is associated with increased levels of vascular endothelial growth factor and macrophage inflammatory protein 1 alpha and is inhibited by blocking activation of microglia.

PVC-211 murine leukemia virus (MuLV) is a neuropathogenic retrovirus that has undergone genetic changes from its nonneuropathogenic parent, Friend MuLV, that allow it to efficiently infect rat brain capillary endothelial cells (BCEC). To clarify the mechanism by which PVC-211 MuLV expression in BCEC induces neurological disease, we examined virus-infected rats at various times during neurological disease progression for vascular and inflammatory changes. As early as 2 weeks after virus infection and before any marked appearance of spongiform neurodegeneration, we detected vessel leakage and an increase in size and number of vessels in the areas of the brain that eventually become diseased. Consistent with these findings, the amount of vascular endothelial growth factor (VEGF) increased in the brain as early as 1 to 2 weeks postinfection. Also detected at this early disease stage was an increased level of macrophage inflammatory protein 1 alpha (MIP-1 alpha), a cytokine involved in recruitment of microglia to the brain. This was followed at 3 weeks postinfection by a marked accumulation of activated microglia in the spongiform areas of the brain accompanied by an increase in tissue plasminogen activator, a product of microglia implicated in neurodegeneration. Pathological observations at the end stage of the disease included loss of neurons, decreased myelination, and mild muscle atrophy. Treatment of PVC-211 MuLV-infected rats with clodronate-containing liposomes, which specifically kill microglia, significantly blocked neurodegeneration. Together, these results suggest that PVC-211 MuLV infection of BCEC results in the production of VEGF and MIP-1 alpha, leading to the vascular changes and microglial activation necessary to cause neurodegeneration.

Best practices in implementing lifestyle interventions in the WISEWOMAN program: adaptable strategies for public health programs.

PURPOSE: Describe best practices for implementing a variety of lifestyle interventions targeting cardiovascular disease risk factors. APPROACH: A mixed-methods approach was used to collect and analyze data. The study was guided by the RE-AIM framework. SETTING: Selected Well-Integrated Screening and Intervention for Women Across the Nation (WISEWOMAN) projects funded by the Centers for Disease Control and Prevention. PARTICIPANTS: Five of the 15 currently operating WISEWOMAN projects were selected for study. Selection was based on availability of quantitative performance data, which were used to identify two high-performing and one low-performing sites within each project. METHOD: Qualitative data collection included a review of program materials; telephone interviews with federal, project, and local staff, and site visits. Site visits involved interviews with staff observations of the lifestyle intervention, and discussions with focus groups of participants. Analysis involved writing site reports, developing theme tables, identifying practices of interest, and applying an algorithm to identify best practices. RESULTS: Eighty-seven best practices were identified. We present a subset of 31 practices applicable to other public health programs and for which differences in how high- and low-performing sites used the practices were identified. DISCUSSION: Many of the best practices identified are applicable to broader audiences. Practitioners interested in strategies to recruit, engage, and retain participants and to facilitate behavior change can learn from these practices.

The tyrosine kinase sf-Stk and its downstream signals are required for maintenance of friend spleen focus-forming virus-induced fibroblast transformation.

Infection of erythroid progenitor cells by Friend spleen focus-forming virus (SFFV) leads to acute erythroid hyperplasia and eventually to erythroleukemia in susceptible strains of mice. The viral envelope protein, SFFV gp55, forms a complex with the erythropoietin receptor (EpoR) and a short form of the receptor tyrosine kinase Stk (sf-Stk), activating both and inducing Epo-independent proliferation. Recently, we discovered that coexpression of SFFV gp55 and sf-Stk is sufficient to transform NIH 3T3 and primary fibroblasts. In the current study, we demonstrate that sf-Stk and its downstream effectors are critical to this transformation. Unlike SFFV-derived erythroleukemia cells, which depend on PU.1 expression for maintenance of the transformed phenotype, SFFV gp55-sf-Stk-transformed fibroblasts are negative for PU.1. Underscoring the importance of sf-Stk to fibroblast transformation, knockdown of sf-Stk abolished the ability of these cells to form anchorage-independent colonies. Like SFFV-infected erythroid cells, SFFV gp55-sf-Stk-transformed fibroblasts express high levels of phosphorylated MEK, ERK, phosphatidylinositol 3-kinase (PI3K), Gab1/2, Akt, Jun kinase (JNK), and STAT3, but unlike virus-infected erythroid cells they fail to express phosphorylated STATs 1 and 5, which may require involvement of the EpoR. In addition, the p38 mitogen-activated protein kinase (MAPK) stress response is suppressed in the transformed fibroblasts. Inhibition of either JNK or the PI3K pathway decreases both monolayer proliferation and anchorage-independent growth of the transformed fibroblasts as does the putative kinase inhibitor luteolin, but inhibition of p38 MAPK has no effect. Our results indicate that sf-Stk is a molecular endpoint of transformation that could be targeted directly or with agents against its downstream effectors.

Erythroblast transformation by the friend spleen focus-forming virus is associated with a block in erythropoietin-induced STAT1 phosphorylation and DNA binding and correlates with high expression of the hematopoietic phosphatase SHP-1.

Infection of mice with Friend spleen focus-forming virus (SFFV) results in a multistage erythroleukemia. In the first stage, the SFFV envelope glycoprotein interacts with the erythropoietin receptor and a short form of the receptor tyrosine kinase sf-Stk, resulting in constitutive activation of signal transducing molecules and the development of erythropoietin (Epo)-independent erythroid hyperplasia and polycythemia. The second stage results from the outgrowth of a rare virus-infected erythroid cell that expresses nonphysiological levels of the myeloid transcription factor PU.1. These cells exhibit a differentiation block and can be grown as murine erythroleukemia (MEL) cell lines. In this study, we examined SFFV MEL cells to determine whether their transformed phenotype was associated with a block in the activation of any Epo signal-transducing molecules. Our studies indicate that Epo- or SFFV-induced activation of STAT1/3 DNA binding activity is blocked in SFFV MEL cells. The block is at the level of tyrosine phosphorylation of STAT1, although Jak2 phosphorylation is not blocked in these cells. In contrast to Epo, alpha interferon can induce STAT1 phosphorylation and DNA binding in SFFV MEL cells. The SFFV-transformed cells were shown to express elevated levels of the hematopoietic phosphatase SHP-1, and treatment of the cells with a phosphatase inhibitor restored STAT1 tyrosine phosphorylation. MEL cells derived from Friend murine leukemia virus (MuLV) or ME26 MuLV-infected mice, which do not express PU.1, express lower levels of SHP-1 and are not blocked in STAT1/3 DNA-binding activity. Our studies suggest that SFFV-infected erythroid cells become transformed when differentiation signals activated by STAT1/3 are blocked due to high SHP-1 levels induced by inappropriate expression of the PU.1 protein.

Feeding Infants and Toddlers Study: do vitamin and mineral supplements contribute to nutrient adequacy or excess among US infants and toddlers?

OBJECTIVE: To report the prevalence of dietary supplement use in a random sample of US infants 4 to 24 months of age, and to compare demographic characteristics, usual nutrient intakes, and food patterns of supplement users and nonusers. DESIGN: Data from 24-hour recalls collected for the 2002 Feeding Infants and Toddlers Study were analyzed. Recalls included nutrient contributions from dietary supplements as well as all foods and beverages. We estimated usual energy and nutrient intakes of supplement users and nonusers, as well as the prevalence of nutrient adequacy and excess in the two groups. We also compared demographic characteristics and food patterns of supplement users and nonusers and, for supplement users, estimated the proportion of total intake provided by foods and the proportion provided by supplements. SUBJECTS: A national random sample of 3,022 infants and toddlers age 4 to 24 months, including 430 vitamin and/or mineral supplement users and 2,592 nonusers. STATISTICAL ANALYSIS: We compared means, percentile distributions, and proportions by age and supplement subgroup, and applied the Dietary Reference Intakes to assess usual nutrient intakes. We conducted regression analysis to determine which population characteristics predict the use of dietary supplements in this population. RESULTS: Overall, 8% of infants age 4 to 5 months received some type of dietary supplement. The prevalence of supplement use increased with age, to 19% among infants 6 to 11 months and 31% among toddlers 12 to 24 months. The vast majority of supplement users (97%) received only one type of supplement, most commonly a multivitamin and/or mineral supplement. Vitamin/mineral supplement use among infants and toddlers was associated with being a first-born child and being reported by the primary caretaker as being a picky eater. Characteristics that were independent predictors of supplement use were living in the Northeast, being male, and living in a household with fewer children. We found no significant differences between supplement users and nonusers in mean daily intakes of nutrients or nutrient density from foods alone, and few differences in food consumption. Overall, the prevalence of inadequate intakes was low (<1% to 2%). However, 65% of supplement nonusers and 9% of supplement users had vitamin E intakes less than the Estimated Average Requirement. Excessive intakes (ie, intakes above the Tolerable Upper Intake Level) were noted for both supplement users and nonusers for vitamin A (97% and 15% of toddlers) and zinc (60% and 59% of older infants and 68% and 38% of toddlers) as well as for folate among supplement users (18% of toddlers). CONCLUSIONS: Generally, healthy infants and toddlers can achieve recommended levels of intake from food alone. Dietetics professionals should encourage caregivers to use foods rather than supplements as the primary source of nutrients in children's diets. Vitamin and mineral supplements can help infants and toddlers with special nutrient needs or marginal intakes achieve adequate intakes, but care must be taken to ensure that supplements do not lead to excessive intakes. This is especially important for nutrients that are widely used as food fortificants, including vitamin A, zinc, and folate.

Feeding Infants and Toddlers Study: meal and snack intakes of Hispanic and non-Hispanic infants and toddlers.

OBJECTIVE: To describe meal and snack patterns of Hispanic and non-Hispanic infants and toddlers. DESIGN: A cross-sectional telephone survey in which mothers or other primary caregivers reported their infants' and toddlers' food and beverage intake for a 24-hour period. SUBJECTS/SETTING: Subjects were a subset of the national random sample of children aged 4-24 months who participated in the 2002 Feeding Infants and Toddlers Study. The Feeding Infants and Toddlers Study includes a stratified random sample of 3,022 infants and toddlers aged 4-24 months. Three hundred seventy-one Hispanic and 2,637 non-Hispanic children who had 24-hour dietary recalls are included in the subset. ANALYSES: Means+/-standard errors of daily intakes of energy, nutrients, and nutrient densities were calculated, as were percentages of children consuming foods at each eating occasion. RESULTS: Hispanic and non-Hispanic infants and toddlers, on average, were fed seven times per day. Overall, the percentages of children who ate snacks increased with age, and more than 80% of toddlers aged 12-24 months consumed afternoon snacks, with more than 90% of Hispanic children consuming an afternoon snack. In each age group, there were significant differences between ethnic groups in nutrient intakes by eating occasion. No significant difference was seen for energy across all meal occasions. At age 6-11 months, Hispanic children had a significantly lower intake of carbohydrate at dinner and lower intake of saturated fat at afternoon snacks compared with non-Hispanic children (P<.05). The main difference between Hispanic children's and non-Hispanic children's intakes by eating occasion is at age 12-24 months. Hispanics aged 12-24 months had significantly (P<.05) lower percentages of energy from fat and saturated fat and a significantly (P<.05) higher percentage of carbohydrate at lunch compared with non-Hispanic children. For dinner, Hispanic toddlers had significantly (P<.05) lower intakes of total fat and saturated fat compared with non-Hispanic toddlers at age 12-24 months. Overall fiber intake contributed 2 g/meal for both ethnic groups. Snacks contributed, on average, less than 1 g fiber, except Hispanic toddlers had significantly higher fiber intake at afternoon snacks (1.5 g) than non-Hispanic toddlers. Foods frequently consumed at meals and snacks were lacking in whole grains, vegetables, and fruits. Most nutrients were not significantly different between Hispanics and non-Hispanics for meals and snacks. CONCLUSIONS: Considering the sizeable contribution that snacks make toward overall energy, parents and caregivers should plan toddlers' snacks to complement meals by including additional fruits, vegetables, and whole grains that are culturally appropriate rather than fruit drinks, cookies, and crackers. This will increase fiber intake and limit fat and sugar intakes. To develop healthful eating patterns, introduce toddlers to foods eight to 10 times to increase food acceptance and the likelihood of establishing healthful eating patterns. Dietetics professionals need to consider cultural differences when developing meal and snack patterns for Hispanic and non-Hispanic infants and toddlers.

Friend spleen focus-forming virus transforms rodent fibroblasts in cooperation with a short form of the receptor tyrosine kinase Stk.

Friend spleen focus-forming virus (SFFV) causes rapid erythroleukemia in mice due to expression of its unique envelope glycoprotein, gp55. Erythroid cells expressing SFFV gp55 proliferate in the absence of their normal regulator erythropoietin (Epo) because of constitutive activation of Epo signal transduction pathways. Although SFFV infects many cell types, deregulation of cell growth occurs only when SFFV infects erythroid cells, suggesting that these cells express unique proteins that the virus requires to mediate its biological effects. Not only do erythroid cells express the Epo receptor (EpoR), but those from mice susceptible to SFFV-induced erythroleukemia also express a short form of the receptor tyrosine kinase Stk (sf-Stk). In erythroid cells, SFFV gp55 interacts with the EpoR complex and sf-Stk, leading to activation of the kinase and constitutive activation of signal transducing molecules. In this study, we demonstrate that SFFV gp55 can also deregulate the growth of nonerythroid cells when it is coexpressed with sf-Stk. Expression of SFFV gp55 in rodent fibroblasts engineered to express sf-Stk induced their transformation, as demonstrated by focus formation and anchorage-independent growth in vitro. This transformation by SFFV gp55 requires the kinase activity of sf-Stk and the presence of its extracellular domain but not expression of the EpoR or the tyrosine kinase Jak2, which is required for activation of signal transduction pathways through the EpoR. Thus, expression of SFFV gp55 in nonerythroid cells coexpressing sf-Stk results in their uncontrolled growth, demonstrating a previously unrecognized mechanism for retrovirus transformation of rodent fibroblasts and providing insight into SFFV-induced disease.

The phenomenology of empowerment in collective action.

Recent research has hypothesized that empowerment can arise from collective action through collective self-objectification (CSO), defined as action that actualizes participants' social identity against the power of dominant groups. Activists (N = 37) described several experiences that made them feel empowered (and disempowered). Among the various explanations they offered for these feelings, the most prominent were CSO, unity, and support (or their absence). CSO was also predictive of reports of positive emotion, although unity was the best predictor of reports of further involvement. Overall, the study suggests that actualizing one's social identity through collective action has personal as well as political significance.

Activation of the Jun N-terminal kinase pathway by friend spleen focus-forming virus and its role in the growth and survival of friend virus-induced erythroleukemia cells.

Members of the mitogen-activated protein kinase (MAPK) family, including Jun amino-terminal kinase (JNK) and extracellular signal-related kinase (ERK), play an important role in the proliferation of erythroid cells in response to erythropoietin (Epo). Erythroid cells infected with the Friend spleen focus-forming virus (SFFV) proliferate in the absence of Epo and show constitutive activation of Epo signal transduction pathways. We previously demonstrated that the ERK pathway was constitutively activated in Friend SFFV-infected erythroid cells, and in this study JNK is also shown to be constitutively activated. Pharmacological inhibitors of both the ERK and JNK pathways stopped the proliferation of primary erythroleukemic cells from Friend SFFV-infected mice, with little induction of apoptosis, and furthermore blocked their ability to form Epo-independent colonies. However, only the JNK inhibitor blocked the proliferation of erythroleukemia cell lines derived from these mice. The JNK inhibitor caused significant apoptosis in these cell lines as well as an increase in the fraction of cells in G(2)/M and undergoing endoreduplication. In contrast, the growth of erythroleukemia cell lines derived from Friend murine leukemia virus (MuLV)-infected mice was inhibited by both the MEK and JNK inhibitors. JNK is important for AP1 activity, and we found that JNK inhibitor treatment reduced AP1 DNA-binding activity in primary erythroleukemic splenocytes from Friend SFFV-infected mice and in erythroleukemia cell lines from Friend MuLV-infected mice but did not alter AP1 DNA binding in erythroleukemia cell lines from Friend SFFV-infected mice. These data suggest that JNK plays an important role in cell proliferation and/or the survival of erythroleukemia cells.

Mass spectrometry of intact ribosomes.

The ability to maintain intact ribosomes in the mass spectrometer has enabled research into their changes in conformation and interactions. In the mass spectrometer, it is possible to induce dissociation of proteins from the intact ribosome and, in conjunction with atomic structures, to understand the factors governing their release. We have applied this knowledge to interpret the structural basis for release of proteins from ribosomes for which no high resolution structures are available, such as complexes with elongation factor G and ribosomes from yeast. We also describe how improvements in technology and understanding have widened the scope of our research and lead to dramatic improvements in quality and information available from spectra of intact ribosomes.

Mass spectrometry of ribosomes from Saccharomyces cerevisiae: implications for assembly of the stalk complex.

The acidic ribosomal P proteins form a distinct protuberance on the 60 S subunit of eukaryotic ribosomes. In yeast this structure is composed of two heterodimers (P1alpha-P2beta and P1beta-P2alpha) attached to the ribosome via P0. Although for prokaryotic ribosomes the isolation of a pentameric stalk complex comprising the analogous proteins is well established, its observation has not been reported for eukaryotic ribosomes. We used mass spectrometry to examine the composition of the stalk proteins on ribosomes from Saccharomyces cerevisiae. The resulting mass spectra reveal a noncovalent complex of mass 77,291 +/- 7 Da assigned to the pentameric stalk. Tandem mass spectrometry confirms this assignment and is consistent with the location of the P2 proteins on the periphery of the stalk complex, shielding the P1 proteins, which in turn interact with P0. No other oligomers are observed, confirming the specificity of the pentameric complex. At lower m/z values the spectra are dominated by individual proteins, largely from the stalk complex, giving rise to many overlapping peaks. To define the composition of the stalk proteins in detail we compared spectra of ribosomes from strains in which genes encoding either or both of the interacting stalk proteins P1alpha or P2beta are deleted. This enables us to define novel post-translational modifications at very low levels, including a population of P2alpha molecules with both phosphorylation and trimethylation. The deletion mutants also reveal interactions within the heterodimers, specifically that the absence of P1alpha or P2beta destabilizes binding of the partner protein on the ribosome. This implies that assembly of the stalk complex is not governed solely by interactions with P0 but is a cooperative process involving binding to partner proteins for additional stability on the ribosome.

Heteronuclear NMR investigations of dynamic regions of intact Escherichia coli ribosomes.

15N-(1)H NMR spectroscopy has been used to probe the dynamic properties of uniformly (15)N labeled Escherichia coli ribosomes. Despite the high molecular weight of the complex ( approximately 2.3 MDa), [(1)H-(15)N] heteronuclear single-quantum correlation spectra contain approximately 100 well resolved resonances, the majority of which arise from two of the four C-terminal domains of the stalk proteins, L7/L12. Heteronuclear pulse-field gradient NMR experiments show that the resonances arise from species with a translational diffusion constant consistent with that of the intact ribosome. Longitudinal relaxation time (T(1)) and T(1 rho) (15)N-spin relaxation measurements show that the observable domains tumble anisotropically, with an apparent rotational correlation time significantly longer than that expected for a free L7/L12 domain but much shorter than expected for a protein rigidly incorporated within the ribosomal particle. The relaxation data allow the ribosomally bound C-terminal domains to be oriented relative to the rotational diffusion tensor. Binding of elongation factor G to the ribosome results in the disappearance of the resonances of the L7/L12 domains, indicating a dramatic reduction in their mobility. This result is in agreement with cryoelectron microscopy studies showing that the ribosomal stalk assumes a single rigid orientation upon elongation factor G binding. As well as providing information about the dynamical properties of L7/L12, these results demonstrate the utility of heteronuclear NMR in the study of mobile regions of large biological complexes and form the basis for further NMR studies of functional ribosomal complexes in the context of protein synthesis.