A distal enhancer region in the human beta-casein gene mediates the response to prolactin and glucocorticoid hormones

The 5' flanking region of the human beta-casein gene was investigated for the presence of regulatory sequences mediating the action of the lactogenic hormones prolactin and dexamethasone. DNA encompassing 9389 base pairs of the flanking region was isolated and a sequence comparison performed with regulatory regions previously identified in the beta-casein gene of rodents and ruminants. The analysis revealed the presence of a distal region between -4700 and -4550 with a high percentage of identity to the bovine beta-casein enhancer region, and a proximal region between -1 and -200 similar to the proximal promoter regions found in rodents and ruminants. Reporter gene constructs under the control of the distal or the proximal region of the human beta-casein gene were tested for their responsiveness to prolactin and dexamethasone. In transfection experiments, the distal region functioned as a lactogenic hormone inducible enhancer, whereas the proximal region exhibited low activity. In electromobility shift assays, multiple binding sites for Stat5, CCAAT/enhancer-binding proteins, and Ets domain proteins were identified in the distal human enhancer. These transcription factors have already been demonstrated as important regulators of the transcription of milk protein genes in rodents. Thus, a common set of transcription factors appears to be required for the expression of the human beta-casein gene and of milk protein genes in other species.

[Unilateral pulmonary vein atresia in early adulthood]

Unilateral pulmonary vein atresia is a rare condition in adults that may cause serious diagnostic problems because of unspecific clinical findings. A 28-year old female patient is described who presented with signs of recurrent pulmonary embolism with shortness of breathing, unilateral thoracic pain and several episodes of haemoptysis. Ventilation and perfusion scans showed a total lack of perfusion in the right lung with only slight disturbance of ventilation. However, no marked increase of pulmonary artery pressure and no signs of a recent thrombosis of peripheral veins were found. Transoesophageal echocardiography and pulmonary angiography in combination with aortography revealed the diagnosis of unilateral pulmonary vein atresia with abnormal branches of bronchial arteries. There is a considerably left-to-right shunt with return of flow from the bronchial arteries to the right and afterwards to the left pulmonary artery. Clinical, radiological and nuclear medical findings as well as therapeutical options are described.

Mechanism of interaction between the glucocorticoid receptor and Stat5: role of DNA-binding

The functional interaction between the glucocorticoid receptor (GR) and the signal transducer and activator of transcription-5 (Stat5) was investigated by studying the synergistic activation of beta-cascin gene transcription by prolactin and glucocorticoids. The synergism was shown to be mediated by a complex hormone response region with multiple binding sites for Stat5, the glucocorticoid receptor, and CCAAT/enhancer binding proteins (C/EBP). HC11 mammary epithelial cells, which contain physiological levels of GR and Stat5, and COS-7 cells overexpressing GR and Stat5 were employed. In both cell types intact binding sites for Stat5 and the GR were a prerequisite for the synergism, whereas C/EBP sites were only required in HC11 cells. Interestingly, the GR sites employed for the synergism were nonclassical, half palindromic sites, which did not function in the absence of activated Stat5 to mediate the action of the GR on transcription. The interaction of GR and Stat5 triggered by the unusual configuration of binding sites appears to represent a novel mechanism by which these two distinct types of transcription factors cooperate. The mode of interaction provides an efficient means to restrict gene expression to conditions where both Stat5 and the GR are activated.

Granulocyte-macrophage colony-stimulating factor induces a unique set of STAT factors in murine dendritic cells

Cytokine-mediated signaling pathways were studied in mouse dendritic cells (DC) by analysis of the activation pattern of STAT factors. Electrophoretic mobility shift assays were performed to detect STAT isoform-specific complexes. Granulocyte-macrophage colony-stimulating factor (GM-CSF) simultaneously induced complexes containing STAT1, STAT3, STAT5A, STAT5B and STAT6. In non-DC, a similar broad activation pattern of STAT factors by GM-CSF or other cytokines has not been observed so far. By comparison, in peritoneal macrophages, GM-CSF induced a complex with the properties of a truncated form of STAT5. Other cytokines tested on DC either failed to induce STAT factors [interleukin (IL)-1 beta, IL-2, IL-15], or activated the same STAT factors as observed in peritoneal macrophages (IL-4, IFN-gamma). Our results implicate a specific effect of GM-CSF on STAT signaling in DC which might account for the cell type-specific effect of this cytokine on development and function.

Promoter-dependent synergy between glucocorticoid receptor and Stat5 in the activation of beta-casein gene transcription

Steroid hormone receptors and Stat factors comprise two distinct families of inducible transcription factors. Activation of a member of each family, namely the glucocorticoid receptor by glucocorticoids and Stat5 by prolactin, is required for the efficient induction of the expression of milk protein genes in the mammary epithelium. We have studied the mode of interaction between Stat5 and the glucocorticoid receptor in the activation of beta-casein gene transcription. The functional role of potential half-palindromic glucocorticoid receptor-binding sites mapped previously in the promoter region was investigated. beta-Casein gene promoter chloramphenicol acetyltransferase constructs containing mutations and deletions in these sites were tested for their responsiveness to the synergistic effect of prolactin and dexamethasone employing COS-7 cells or HC11 mammary epithelial cells. Synergism depended on promoter regions containing intact binding sites for the glucocorticoid receptor and Stat5. The carboxyl-terminal transactivation domains of Stat5a and Stat5b were not required for this synergism. Our results suggest that in lactogenic hormone response elements glucocorticoid receptor molecules bound to nonclassical half-palindromic sites gain competence as transcriptional activators by the interaction with Stat5 molecules binding to vicinal sites.

[Why do adults with mucoviscidosis refuse a medically recommended course of intravenous antibiotic therapy?]

BACKGROUND

Regular courses of intravenous antibiotics are recommended for the treatment of chronic Pseudomonas aeruglnosa (PA) infection in patients with cystic fibrosis. We report the results of interviews performed to evaluate why a subgroup of patients vote against regular intravenous (i.v.) antibiotic treatment.

METHODS

Structured interviews covering a) the individual's perception of chronic PA infection, b) the patient's expectations regarding the effectiveness of i.v. treatment, c) the patient's personal reasons for refusal of i.v. treatment. STUDY COHORT: 16 out of 18 adult patients treated in the adult CF outpatient clinic at Hannover Medical School who had voted against the physician's recommendation to receive regular i.v. therapy twice a year.

RESULTS

More than one half of the patients did not regard chronic PA infection as important due to the lack of specific symptoms. A subgroup of patients had no idea of what their clinical status should be if i.v. antibiotics would be necessary; these patients reported prior experience of treatment courses which had been ineffective and had been instituted after talking into the patients. The most frequent reasons against IV treatment were not being sick enough and fear of adverse drug effects.

ASSESSMENT

The results are being discussed considering the physician-patient relationship. The reasons why patients refuse help should be extensively explored rather than simply addressing this attitude as "non-compliance". Patients, too, come to reasonable decisions, and it is important to know their thoughts and reasoning if one intends to influence them.

Comparative study on the phosphotyrosine motifs of different cytokine receptors involved in STAT5 activation

Several cytokines and growth factors activate transcription of their target genes via the JAK/STAT signalling pathway. It has been shown that the interaction between SH2 domains of STAT factors and receptor phosphotyrosine residues plays an essential role in the specific recruitment of STATs. For STAT5, however, the importance of receptor tyrosines is still controversial. Using a chimeric receptor system in COS-7 cells, we studied the activation of STAT5 through the interleukin-6 signal transducer gp130. In contrast to previous reports, we did not detect gp130-mediated STAT5 activation. However, STAT5 activation was achieved when tyrosine motifs of other cytokine receptors were fused to the membrane-proximal part of gp130. The comparison of the relative potency of different tyrosine motifs revealed that hydrophobic amino acids, preferentially leucine, in positions +1 and +3, and an aspartate residue in position -1 or -2 with respect to the tyrosine are likely to be required for efficient STAT5 recruitment. In summary, we show here for the first time that phosphotyrosine motifs can confer the ability to activate STAT5 to a heterologous receptor.

Circulating complement proteins in patients with sepsis or systemic inflammatory response syndrome

The systemic inflammatory response of the body to invading microorganisms, termed sepsis, leads to profound activation of the complement system. Pathophysiological concepts suggest that complement activation occurs very early in this syndrome. Thus, we discuss whether the determination of concentrations of the complement components C3a, C5a, and C3 in plasma as well as of the C3a/C3 ratio might be helpful to diagnose sepsis early. For this purpose, 33 patients from an intensive care unit were monitored for 10 days. In comparison with healthy donors, C3a levels and the C3a/C3 ratio of intensive-care-unit patients were significantly elevated (P < 0.0001) on admission. In contrast, C3 levels were significantly reduced (P < 0.0001) but increased during the study. C5a levels in the plasma of healthy donors and patients were identical. Twenty-two of 33 patients fulfilled microbiological and clinical criteria of sepsis. Eleven patients had signs of systemic inflammatory response syndrome but no microbiological evidence of sepsis. The groups could be differentiated from each other by their C3a levels or their C3a/C3 ratios during the first 24 h after the clinical onset of sepsis (P < 0.05). Septic patients in shock had higher C3a levels than normotensive septic patients, although the differences were not significant. Nonsurvivors had significantly higher C3a levels on admission than survivors (P = 0.0185). No differences were found between septic patients who developed adult respiratory distress syndrome and those who did not. Thus, determination of C3a concentrations in plasma may prove useful (i) to diagnose sepsis early, (ii) to differentiate between patients with sepsis and those with systemic inflammatory response syndrome, and (iii) to assess prognosis.

CCAAT/enhancer-binding protein isoforms beta and delta are expressed in mammary epithelial cells and bind to multiple sites in the beta-casein gene promoter

Lactogenic hormone-dependent expression of the rat beta-casein gene in mammary epithelial cells is controlled via a complex regulatory region in the promoter. The sequence between -176 and -82 is the minimal region to confer the response to glucocorticoid hormone and prolactin on a heterologous promoter. The response is further enhanced by the region between -282 and -176. DNase I footprinting experiments and electromobility shift assays revealed the presence of four binding sites for CCAAT/enhancer-binding protein (C/EBP) isoforms in the hormone response region between -220 and -132. In nuclear extracts from mammary epithelial cells, the prevalent C/EBP isoform binding to these sites is beta (C/EBP-beta). C/EBP-delta is also present in mammary epithelial cells, whereas C/EBP-alpha is not detectable. The C/EBP sites are located in close proximity to the previously characterized binding sites for the prolactin-inducible mammary gland factor/signal transducer and activator of transcription-5, the nuclear factor YY1, and the glucocorticoid receptor. The importance of the two proximal C/EBP binding sites at the 5' border of the minimal region was tested by mutational analysis. Mutations of each site were found to inhibit strongly both the basal and the lactogenic hormone-induced transcription of a beta-casein gene promoter chloramphenicol acetyltransferase construct. The results implicate C/EBPs as important regulators of beta-casein gene expression in the mammary epithelium.

Prolactin-dependent activation of a tyrosine phosphorylated DNA binding factor in mouse mammary epithelial cells

The mammary gland factor MGF has been described as a developmentally and environmentally regulated nuclear factor required for transcription of the milk protein gene beta-casein. In the current study the individual role of lactogenic hormones in the activation of MGF DNA binding and the functional relation of MGF to known transcription factors was investigated by electrophoretic mobility shift assays. DNA binding of MGF was rapidly induced by PRL in mammary epithelial cells. The activation was not inhibited by the protein synthesis inhibitor cycloheximide. The effect of PRL on MGF did not require costimulation of cells with the other lactogenic hormones, insulin, and glucocorticoids. Thus, MGF is the first example of a nuclear factor directly regulated by PRL. The MGF complexes formed upon initiation of lactation in the mammary gland and upon stimulation of mammary epithelial cells with PRL migrated at the same position in electrophoretic mobility shift assay, whereas the MGF complex found in mammary gland extracts of pregnant mice exhibited a faster mobility. In cell cultures, PRL-induced activation of MGF as well as up-regulation of beta-casein gene transcription was confined to confluent cultures of mammary epithelial cells and inhibited by long term incubation of cells with epidermal growth factor. MGF was found to be related to the nuclear factors that are activated by tyrosine phosphorylation when cells are stimulated with interferons or cytokines. This notion is supported by experimental evidence for phosphorylation of MGF on tyrosine and by the similar DNA recognition motifs of MGF and cytokine-activated factors.

Involvement of Ets-related proteins in hormone-independent mammary cell-specific gene expression

Regulatory regions have been located in the 5' flanking sequence of the mouse whey acidic protein gene which contribute to its tissue- and stage-specific expression in the mammary gland. They can be functionally separated into elements which mediate the action of lactogenic hormones prolactin and glucocorticoids and elements which control mammary cell-specific transcription in the absence of hormones. By mutational analysis, we have located a site in the whey acidic protein promoter between -120 and -100 which is important for hormone-independent promoter function. In stably transfected HC11 mammary epithelial cells, the hormone-independent activity of the mutated promoter was reduced 40-fold, whereas the capability to respond to lactogenic hormones was retained. The site was specifically recognised by two nuclear factors contained in extracts of cultivated mammary epithelial cells or mammary glands. Electrophoretic mobility shift assay, DNase I footprinting and methylation interference experiments indicated a relation of both factors to the Ets family of DNA-binding proteins. One of these factors also recognised a functionally important site in the mammary cell-specific enhancer of the mouse mammary tumor virus long terminal repeat. The results suggest that factors related to the Ets family are important determinants in mammary cell-specific gene expression.

Glucocorticoid receptor binding sites in the promoter region of milk protein genes

The action of glucocorticoids on the induction of the two milk protein genes beta-casein and whey acidic protein (WAP) is delayed and appears to be indirect. The response requires a co-stimulation of cells with prolactin, is restricted to mammary epithelial cells and is dependent on cis-acting sequences localized in the promoter region of the two genes. We have searched for glucocorticoid receptor (GR) binding sites in these hormone response regions. In vitro DNaseI footprinting experiments were performed with a purified preparation of the GR from rat liver. The sequences between -231 and -7 and between -250 and -79 of mouse WAP and rat beta-casein gene promoter, respectively, were found to contain multiple sites which were protected from the attack of DNaseI by the GR preparation. The sites comprise sequence motifs related to the delayed secondary glucocorticoid response elements described (Chan et al., J. Biol. Chem. 266, 22,634-22,644, 1991), which represent half sites of classical GR binding sites. In the WAP gene promoter, the motifs are arranged head to tail with irregular spacing. The GR binding sites are in close proximity or even overlap with the bindings sites for candidate factors involved in mammary cell specific gene expression. The results suggest a direct co-operation between GR and mammary cell specific transcription factors in mediating the expression of milk protein genes.