Transcriptional activation of human adult alpha-globin genes by hypersensitive site-40 enhancer: function of nuclear factor-binding motifs occupied in erythroid cells.

The developmental stage- and erythroid lineage-specific activation of the human embryonic zeta- and fetal/adult alpha-globin genes is controlled by an upstream regulatory element [hypersensitive site (HS)-40] with locus control region properties, a process mediated by multiple nuclear factor-DNA complexes. In vitro DNase I protection experiments of the two G+C-rich, adult alpha-globin promoters have revealed a number of binding sites for nuclear factors that are common to HeLa and K-562 extracts. However, genomic footprinting analysis has demonstrated that only a subset of these sites, clustered between -130 and +1, is occupied in an erythroid tissue-specific manner. The function of these in vivo-occupied motifs of the alpha-globin promoters, as well as those previously mapped in the HS-40 region, is assayed by site-directed mutagenesis and transient expression in embryonic/fetal erythroid K-562 cells. These studies, together with our expression data on the human embryonic zeta-globin promoter, provide a comprehensive view of the functional roles of individual nuclear factor-DNA complexes in the final stages of transcriptional activation of the human alpha-like globin promoters by the HS-40 element.

Growth factors can enhance lymphocyte survival without committing the cell to undergo cell division.

Growth factors have been defined by their ability to promote the proliferative expansion of receptor-bearing cells. For example, antigen-activated T cells expressing the alpha beta gamma form of the interleukin 2 (IL-2) receptor will proliferate in response to IL-2. In contrast, resting T cells, which express the IL-2 receptor beta and gamma chains, do not proliferate in response to IL-2. We demonstrate that the survival of resting T cells following gamma irradiation is greatly enhanced by pretreatment with IL-2. The radioprotective effect of IL-2 is dose dependent, does not result from the induction of cell proliferation, and does not require expression of the IL-2 receptor alpha chain. Thus, the beta gamma IL-2 receptor expressed on resting T cells can transduce signals that promote cell survival without committing the T cell to undergo cell division. IL-4 and IL-7, but not IL-1, IL-3, or IL-6, were also found to enhance the survival of quiescent T cells following gamma irradiation. Thus, certain growth factor-receptor interactions can serve to maintain cell viability in a manner that is independent of their ability to initiate or maintain cell proliferation. These data may have important implications for the use of growth factors in patients being treated with radiation and/or chemotherapy.

Transplantation of a 17-amino acid alpha-helical DNA-binding domain into an antibody molecule confers sequence-dependent DNA recognition.

Recombinant antibodies capable of sequence-specific interactions with nucleic acids represent a class of DNA- and RNA-binding proteins with potential for broad application in basic research and medicine. We describe the rational design of a DNA-binding antibody, Fab-Ebox, by replacing a variable segment of the immunoglobulin heavy chain with a 17-amino acid domain derived from TFEB, a class B basic helix-loop-helix protein. DNA-binding activity was studied by electrophoretic mobility-shift assays in which Fab-Ebox was shown to form a specific complex with DNA containing the TFEB recognition motif (CACGTG). Similarities were found in the abilities of TFEB and Fab-Ebox to discriminate between oligodeoxyribonucleotides containing altered recognition sequences. Comparable interference of binding by methylation of cytosine residues indicated that Fab-Ebox and TFEB both contact DNA through interactions along the major groove of double-stranded DNA. The results of this study indicate that DNA-binding antibodies of high specificity can be developed by using the modular nature of both immunoglobulins and transcription factors.

Differential tubulogenic and branching morphogenetic activities of growth factors: implications for epithelial tissue development.

At least two kidney epithelial cell lines, the Madin-Darby canine kidney (MDCK) and the murine inner medullary collecting duct line mIMCD-3, can be induced to form branching tubular structures when cultured with hepatocyte growth factor (HGF) plus serum in collagen I gels. In our studies, whereas MDCK cells remained unable to form tubules in the presence of serum alone, mIMCD-3 cells formed impressive branching tubular structures with apparent lumens, suggesting the existence of specific factors in serum that are tubulogenic for mIMCD-3 cells but not for MDCK cells. Since normal serum does not contain enough HGF to induce tubulogenesis, these factors appeared to be substances other than HGF. This was also suggested by another observation: when MDCK cells or mIMCD-3 cells were cocultured under serum-free conditions with the embryonic kidney, both cell types formed branching tubular structures similar to those induced by HGF; however, only in the case of MDCK cells could this be inhibited by neutralizing antibodies against HGF. Thus, the embryonic kidney produces growth factors other than HGF capable of inducing tubule formation in the mIMCD-3 cells. Of a number of growth factors examined, transforming growth factor alpha (TGF-alpha) and epidermal growth factor (EGF) were found to be tubulogenic for mIMCD-3 cells. Whereas only HGF was a potent tubulogenic factor for MDCK cells, HGF, TGF-alpha, and EGF were potent tubulogenic factors for mIMCD-3 cells. Nevertheless, there were marked differences in the capacity of these tubulogenic factors to induce tubulation as well as branching events in those tubules that did form (HGF >> TGF-alpha > EGF). Thus, at least three different growth factors can induce tubulogenesis and branching in a specific epithelial cell in vitro (though to different degrees), and different epithelial cells that are capable of forming branching tubular structures demonstrate vastly different responses to tubulogenic growth factors. The results are discussed in the context of branching morphogenesis during epithelial tissue development.

Induction of cell proliferation in mammalian inner-ear sensory epithelia by transforming growth factor alpha and epidermal growth factor.

Regenerative proliferation occurs in the inner-ear sensory epithelial of warm-blooded vertebrates after insult. To determine how this proliferation is controlled in the mature mammalian inner ear, several growth factors were tested for effects on progenitor-cell division in cultured mouse vestibular sensory epithelia. Cell proliferation was induced in the sensory epithelium by transforming growth factor alpha (TGF-alpha) in a dose-dependent manner. Proliferation was also induced by epidermal growth factor (EGF) when supplemented with insulin, but not EGF alone. These observations suggest that stimulation of the EGF receptors by TGF-alpha binding, or EGF (plus insulin) binding, stimulates cell proliferation in the mature mammalian vestibular sensory epithelium.

IGF-1 phosphorylates AMPK-alpha subunit in ATM-dependent and LKB1-independent manner

Serine/threonine protein kinase AMP-activated protein kinase (AMPK) is a key metabolic stress-responsive factor that promotes the adaptation of cells to their microenvironment. Elevated concentrations of intracellular AMP, caused by metabolic stress, are known to activate AMPK by phosphorylation of the catalytic subunit. Recently, the tumor suppressor serine/threonine protein kinase LKB1 was identified as an upstream kinases, AMPKKs. In the current study, we found that stimulation with growth factors also caused AMPK-alpha subunit phosphorylation. Interestingly, even an LKB1-nonexpressing cancer cell line, HeLa, exhibited growth factor-stimulated AMPK-alpha subunit phosphorylation, suggesting the presence of an LKB1-independent pathway for AMPK-alpha subunit phosphorylation. In the human pancreatic cancer cell line PANC-1, AMPK-alpha subunit phosphorylation promoted by IGF-I was suppressed by antisense ataxia telangiectasia mutated (ATM) expression. We found that IGF-1 also induced AMPK-alpha subunit phosphorylation in the human normal fibroblast TIG103 cell line, but failed to do so in a human fibroblast AT2-KY cell line lacking ATM. Immunoprecipitates of ATM collected from IGF-1-stimulated cells also caused the phosphorylation of the AMPK-alpha subunit in vitro. IGF-1-stimulated ATM phosphorylation at both threonine and tyrosine residues, and our results demonstrated that the phosphorylation of tyrosine in the ATM molecule is important for AMPK-alpha subunit phosphorylation during IGF-1 signaling. These results suggest that IGF-1 induces AMPK-alpha subunit phosphorylation via an ATM-dependent and LKB1-independent pathway. (C) 2004 Elsevier Inc. All rights reserved.

Role of dietary factors in the development of basal cell cancer and squamous cell cancer of the skin

The role of dietary factors in the development of skin cancer has been investigated for many years; however, the results of epidemiologic studies have not been systematically reviewed. This article reviews human studies of basal cell cancer (BCC) and squamous cell cancer (SCC) and includes all studies identified in the published scientific literature investigating dietary exposure to fats, retinol, carotenoids, vitamin E, vitamin Q and selenium. A total of 26 studies were critically reviewed according to study design and quality of the epidemiologic evidence. Overall, the evidence suggests a positive relationship between fat intake and BCC and SCC, an inconsistent association for retinol, and little relation between beta-carotene and BCC or SCC development. There is insufficient evidence on which to make a judgment about an association of other carotenoids with skin cancer. The evidence for associations between vitamin E, vitamin C, and selenium and both BCC and SCC is weak. Many of the existing studies contain limitations, however, and further well-designed and implemented studies are required to clarify the role of diet in skin cancer. Additionally, the role of other dietary factors, such as flavonoids and other polyphenols, which have been implicated in skin cancer development in animal models, needs to be investigated.

Peroxisome proliferator-activated receptor alpha expression is regulated by estrogen receptor alpha and modulates the response of MCF-7 cells to sodium butyrate

Peroxisome proliferator-activated receptors are ligand-activated transcription factors with a potential role in cancer. We investigated peroxisome proliferator-activated receptor alpha expression in breast cancer cell lines and showed a relationship between mean peroxisome proliferator-activated receptor alpha and estrogen receptor alpha mRNA levels in estrogen receptor alpha positive breast cancer cells. Transfection of estrogen receptor alpha into the estrogen receptor alpha negative cell line, MDA-MB-231 decreased peroxisome proliferator-activated receptor a mRNA and conversely inhibition of estrogen receptor alpha by ICI-182 780 in estrogen receptor a positive, MCF-7 cells increased peroxisome proliferator-activated receptor a mRNA levels. Estrogen receptor alpha levels can be modulated by histone deacetylase inhibitors and such agents are in clinical trials for cancer treatment. We found the histone deacetylase inhibitor, sodium butyrate, increased peroxisome proliferator-activated receptor alpha mRNA levels within 4 h of treatment. Peroxisome proliferator-activated receptor a modulation was independent of estrogen receptor alpha, as a similar increase was observed in the estrogen receptor a negative MDA-MB-231 cells. To further investigate the relationship between sodium butyrate and peroxisome proliferator-activated receptor alpha expression, we created an MCF-7 cell line that conditionally over-expresses human peroxisome proliferator-activated receptor alpha. Over-expression of the peroxisome proliferator-activated receptor protected MCF-7 cells from sodium butyrate-mediated inhibition of proliferation and attenuated sodium butyrate-mediated induction of histone deacetylase 3 mRNA, indicating that elevated levels of peroxisome proliferator-activated receptor alpha may reduce the sensitivity of cells to histone deacetylase inhibitors. The estrogen receptor alpha dependence of peroxisome proliferator-activated receptor alpha levels may be significant since estrogen receptor alpha negative breast cancer cells are associated with a more aggressive phenotype. Our studies also suggest that peroxisome proliferator-activated receptor alpha levels may be a marker of breast cancer cell sensitivity to histone deacetylase inhibitors. (c) 2004 Elsevier Ltd. All rights reserved.

The chicken ovalbumin upstream promoter-transcription factors modulate genes and pathways involved in skeletal muscle cell metabolism

The chicken ovalbumin upstream promoter-transcription factors ( COUP-TFs) are orphan members of the nuclear hormone receptor ( NR) superfamily. COUP-TFs are involved in organogenesis and neurogenesis. However, their role in skeletal muscle ( and other major mass tissues) and metabolism remains obscure. Skeletal muscle accounts for similar to 40% of total body mass and energy expenditure. Moreover, this peripheral tissue is a primary site of glucose and fatty acid utilization. We utilize small interfering RNA ( siRNA)-mediated attenuation of Coup-TfI and II ( mRNA and protein) in a skeletal muscle cell culture model to understand the regulatory role of Coup-Tfs in this energy demanding tissue. This targeted NR repression resulted in the significant attenuation of genes that regulate lipid mobilization and utilization ( including Ppar alpha, Fabp3, and Cpt-1). This was coupled to reduced fatty acid beta-oxidation. Additionally we observed significant attenuation of Ucp1, a gene involved in energy expenditure. Concordantly, we observed a 5-fold increase in ATP levels in cells with siRNA-mediated repression of Coup-TfI and II. Furthermore, the expression of classical liver X receptor ( LXR) target genes involved in reverse cholesterol transport ( Abca1 and Abcg1) were both significantly repressed. Moreover, we observed that repression of the Coup-Tfs ablated the activation of Abca1, and Abcg1 mRNA expression by the selective LXR agonist, T0901317. In concordance, Coup-Tf-siRNA-transfected cells were refractory to Lxr-mediated reduction of total intracellular cholesterol levels in contrast to the negative control cells. In agreement Lxr-mediated activation of the Abca1 promoter in Coup-Tf-siRNA cells was attenuated. Collectively, these data suggest a pivotal role for Coup-Tfs in the regulation of lipid utilization/cholesterol homeostasis in skeletal muscle cells and the modulation of Lxr-dependent gene regulation.

Dietary enrichment by almond supplementation: effects on risk factors for cardiovascular disease

Cardiovascular disease (CVD) is the leading cause of death in Europe responsible for more than 4.3 million deaths annually. The World Health Organisation funded the Monica project (1980s-1990s) which monitored ten million subjects aged 22-6Syrs, and demonstrated that coronary heart disease (CHD) mortality declined over 10 years, was due in two thirds of cases to reduced incidence of CHD (reduced risk behaviours e.g. poor diet and smoking) and one third by improved treatments. Epidemiological evidence suggests diets rich in antioxidants decrease incidence of CVD. Regular consumption of nuts, rich in vitamin E and polyphenols reduces atherosclerosis, an important risk for heart disease. Intervention studies to date using alpha tocopherol (an active component of vitamin E) have not consistently proved beneficial. This thesis aims to investigate the effect of almond supplementation on vascular risk factors in healthy young males (18-3Syrs); mature males and female(>SOyrs); and males considered at increased risk of CVD (18-3Syrs) in a cohort of 67 subjects. The effects of almond intake were assessed after 2Sg/d for four weeks followed by SOg/d for four weeks and compared to a control group which did not consume almonds or change their diet. Cardiovascular risk was assessed by plasma lipid profiles, apolipoprotein A1, plasma nitrates/nitrates, vascular flow, BMl, blood pressure, sVCAM-1 and protein oxidation. Systolic and diastolic blood pressures were reduced in almond supplemented volunteers but not in controls. Dietary monounsaturated fatty acids, polyunsaturated fatty acid content and total dietary fats were increased by almond supplementation. Neither sVCAM-1, venous occlusion plethysmography nor plasma nitrite levels were affected by almond intake in any independent group. No significant changes in plasma lipids, and apolipoprotein A1 were observed. In conclusion almonds supplementation caused a reduction in blood pressure that may be due to increased sensitivity of the baroreceptors after increased monounsaturated fatty acid intake.

Paradox lost? Exploring the role of alpha oscillations during externally vs. internally directed attention and the implications for idling and inhibition hypotheses

Although slow waves of the electroencephalogram (EEG) have been associated with attentional processes, the functional significance of the alpha component in the EEG (8.1–12 Hz) remains uncertain. Conventionally, synchronisation in the alpha frequency range is taken to be a marker of cognitive inactivity, i.e. ‘cortical idling’. However, it has been suggested that alpha may index the active inhibition of sensory information during internally directed attentional tasks such as mental imagery. More recently, this idea has been amended to encompass the notion of alpha synchronisation as a means of inhibition of non-task relevant cortical areas irrespective of the direction of attention. Here we test the adequacy of the one idling and two inhibition hypotheses about alpha. In two experiments we investigated the relation between alpha and internally vs. externally directed attention using mental imagery vs. sensory-intake paradigms. Results from both experiments showed a clear relationship between alpha and both attentional factors and increased task demands. At various scalp sites alpha amplitudes were greater during internally directed attention and during increased load, results incompatible with alpha reflecting cortical idling and more in keeping with suggestions of active inhibition necessary for internally driven mental operations.

Assessing administrative and political factors in implementing a living wage ordinance

Since 2000, the number of living wage ordinances has steadily increased throughout the country. While most of the current research has focused on the beneficial outcomes of living wages, little has been published on their administrative practices. To address this shortcoming, this study focused on the identification of key administrative and political factors involved impacting the implementation of living wage ordinances in Miami-Dade and Broward Counties. The study utilized a triangulation of interviews, surveys, and direct observation. The author conducted interviews of administrators and members of the living wage oversight boards in both counties and observed the monthly meetings held by each county's oversight board from January 2006 to June 2007. These findings were buttressed with a national survey of senior staff in other living wage communities. The study utilized descriptive statistics, Chi Square, Cronbach's Alpha, and Spearman's Rank Correlation Coefficient (Spearman's rho). Interviews indicated that administrators in Dade and Broward are seriously under-staffed and budgeted. Ambiguities in the enabling ordinances have lead to loopholes that undermine implementation and accountability for participating contractors. Survey results showed that policy ambiguity, organizational politics, and a lack of organizational capacity were significant negative factors in the implementation process while an organizational culture emphasizing consistent enforcement was a positive factor. Without the proper inputs, an organization hinders itself from meeting its outputs and outcomes. This study finds that Broward and Miami-Dade Counties do not provide the necessary administrative support to implement a living wage effectively – in stark contrast to the high hopes and strong political support behind their passage. For a living wage to succeed, it first needs an organizational culture committed to providing the necessary resources for implementation as well as transparent, consistent accountability mechanisms.

Assessing Administrative and Political Factors in Implementing a Living Wage Ordinance

Since 2000, the number of living wage ordinances has steadily increased throughout the country. While most of the current research has focused on the beneficial outcomes of living wages, little has been published on their administrative practices. To address this shortcoming, this study focused on the identification of key administrative and political factors involved impacting the implementation of living wage ordinances in Miami-Dade and Broward Counties. The study utilized a triangulation of interviews, surveys, and direct observation. The author conducted interviews of administrators and members of the living wage oversight boards in both counties and observed the monthly meetings held by each county’s oversight board from January 2006 to June 2007. These findings were buttressed with a national survey of senior staff in other living wage communities. The study utilized descriptive statistics, Chi Square, Cronbach’s Alpha, and Spearman’s Rank Correlation Coefficient (Spearman’s rho). Interviews indicated that administrators in Dade and Broward are seriously under-staffed and budgeted. Ambiguities in the enabling ordinances have lead to loopholes that undermine implementation and accountability for participating contractors. Survey results showed that policy ambiguity, organizational politics, and a lack of organizational capacity were significant negative factors in the implementation process while an organizational culture emphasizing consistent enforcement was a positive factor. Without the proper inputs, an organization hinders itself from meeting its outputs and outcomes. This study finds that Broward and Miami-Dade Counties do not provide the necessary administrative support to implement a living wage effectively – in stark contrast to the high hopes and strong political support behind their passage. For a living wage to succeed, it first needs an organizational culture committed to providing the necessary resources for implementation as well as transparent, consistent accountability mechanisms.

Modulation of the actin cytoskeleton in the folliculo-stellate cell line TtT/GF by serum factors

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Modulation of the actin cytoskeleton in the folliculo-stellate cell line TtT/GF by serum factors

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.