Global regulatory systems operating in Bacilysin biosynthesis in Bacillus subtilis

In Bacillus subtilis, bacilysin is a nonribosomally synthesized dipeptide antibiotic composed of L-alanine and L-anticapsin. The biosynthesis of bacilysin depends on the bacABCDEywfG operon (bac operon)and the adjacent ywfH gene. To elucidate the effects of global regulatory genes on the expression of bac operon, we used the combination of lacZ fusion analysis and the gel mobility shift assays. The cell density-dependent transition state induction of the bac operon was clearly shown. The basal expression level of the bac operon as well as transition state induction of bac is directly ComA dependent. Three Phr peptides, PhrC, PhrF and PhrK, are required for full-level expression of ComA-dependent bac operon expression, but the most important role seemed to be played by PhrC in stimulating bac expression through a RapC-independent manner. Spo0A is another positive regulator which participates in the transition state induction of bac both directly by interacting with the bac promoter and indirectly by repressing abrB expression. AbrB and CodY proteins do not only directly repress the bac promoter, but they also mutually stimulate the transition state induction of bac indirectly, most likely by antagonizing their repressive effects without preventing each other's binding since both proteins can bind to the bac promoter simultaneously.     

Folic acid inhibition of EGFR-mediated proliferation in human colon cancer cell lines

Althoughaccumulating evidence suggests a chemopreventive role for folic acid incolon cancer, the regulation of this process in unknown. We hypothesizethat supplemental folic acid exerts its chemopreventive role byinhibiting mucosal hyperproliferation, an event considered to becentral to the initiation of carcinogenesis in the gastrointestinaltract. The present investigation examines the effect of supplementalfolic acid on proliferation of Caco-2 and HCT-116 colon cancer celllines. Furthermore, because certain tyrosine kinases, particularlyepidermal growth factor receptor (EGFR), play a role in regulating cellproliferation, we also examined the folic acid-induced changes intyrosine kinase activity and expression of EGFR. In Caco-2 and HCT-116cells, maintained in RPMI 1640 medium containing 1 µg/ml folic acid,we observed that the supplemental folic acid inhibited proliferation ina dose-dependent manner. Pretreatment of HCT-116 and Caco-2 cell lineswith supplemental folic acid (1.25 µg/ml) completely abrogated transforming growth factor- (TGF-)-induced proliferation in bothcell lines. Tyrosine kinase activity and the relative concentration ofEGFR were markedly diminished in both cell lines following a 24-hexposure to supplemental folic acid. The folic acid-induced inhibitionof EGFR tyrosine kinase activity in colon cancer cell lines was alsoassociated with a concomitant reduction in the relative concentrationof the 14-kDa membrane-bound precursor form of TGF-. In conclusion,our data suggest that supplemental folic acid is effective in reducingproliferation in two unrelated colon cancer cell lines and that EGFRtyrosine kinase appears to be involved in regulating this process.

     

The effects of cholesterol oxidation products in sickle and normal red blood cell membranes.

The oxysterol content in normal and sickle red blood cell (RBC) membranes was assessed using thin-layer chromatography and capillary gas chromatography/mass spectrometry. Several more oxysterols were present in sickle RBCs compared to normal RBCs. Sickle RBC membranes had a higher concentration of 5 alpha,6 alpha-epoxycholesterol, 5 alpha-cholestane-3 beta,5,6 beta-triol, 7-ketocholesterol and 19-hydroxycholesterol than normal RBC membranes. The increased oxysterols in sickle RBC may be an effect of the increased oxidative stress which occurs in sickle RBC membranes. Physical characteristics of normal and sickle RBC membrane ghosts with and without inserted oxysterols were examined by Fourier transform infrared spectroscopy. The data are consistent with a greater sterol content in sickle cells compared to normal RBC membranes, and a possible oxysterol-cholesterol synergism.     

Effect of cycline D1 (CCND1) gene polymorphism on tumor formation and behavior in patients with prolactinoma

The objective of this study was to investigate the effect of G870A gene polymorphism of CCND1 on the formation and behavioral features of prolactinomas. One hundred and thirteen patients with prolactinoma and 108 age and gender matched control were included in the study. The patients were divided into two groups as noninvasive and invasive tumors. CCND1 G870A gene polymorphism was compared in patients/control and invasive/noninvasive groups. A and G allele frequencies were found as 41.7% and 58.3% in the controls, and 61.1% and 38.9% in the patients (p<0.01). Rates of G/G, G/A and A/A genotypes were found as 11.8%, 55.9% and 32.4% in the noninvasive group, and 15.6%, 44.4% and 40.0% in the invasive group, respectively. Differences between patient and control groups were significant but were not between invasive and noninvasive groups in terms of the allele frequencies and genotype distribution. Mean tumor size and serum levels of prolactin at the time of diagnosis and change in these values after the treatment were not found statistically significant in genotype subgroups. CCND1 G870A gene polymorphism may be an important factor in the early stages of the tumor formation. However, it did not affect the features of the tumor.     

Effects of salinity on the contents of polyamines and some other compounds in sunflower plants differing in salt tolerance

The effects of salt stress (50, 100, and 150 mM NaCl) on the levels of free, bound, and total polyamines were studied in the leaf tissues of salt-tolerant (Coban) and salt-sensitive (Sanbro) cultivars of sunflower (Helianthus annuus L.) plants grown for 15 or 25 days under salinity. The amounts of free, acid-soluble bound, and total spermine increased in leaf tissues of sunflower plants subjected to salt stress while the levels of other polyamines decreased or no significant changes occurred. The increase in some PA titers suggests their potential role in overcoming the adverse effect of salinity stress. The salt sensitivity of the sunflower plants was associated with the excessive accumulation of total polyamines in the leaf tissues of salt-sensitive cultivar (Sanbro) under saline condition. The content of other compounds such as proline, protein, and ions (Na⁺, K⁺, Cl^-, K⁺/Na⁺) in leaf tissue changed depending on salt concentration and the cultivars used.From Fiziologiya Rastenii, Vol. 52, No. 1, 2005, pp. 36–42.Original English Text Copyright © 2005 by Mutlu, Bozcuk.This article was presented by the authors in English.     

Glow-discharge treated piezoelectric quartz crystals as immunosensors for HSA detection

The aim of this study is to develop an immunoaffinity sensor based on piezoelectric crystals for human serum albumin (HSA) detection in aqueous media. Quartz crystals were treated with ethylene diamine (EDA) plasma in a glow-discharge apparatus in order to substitute amino groups on their surfaces. Then anti-HSA antibodies were immobilized via these amino groups by using glutaraldehyde (GA) as cross-linker. Immobilization of the antibody on the quartz crystal was examined for different pH, antibody concentration and treatment time. The optimum conditions for anti-HSA immobilization were evaluated by the measurements of the activity of the surface against HSA. The optimum values of pH, antibody concentration and treatment time were found 6.2, 0.15 mg/ml and 2 h, respectively. For detection of HSA into the solution, two methods were used. In the first (dip and dry) method, the frequency shifts were measured in air after the 1 h interaction of the anti-HSA immobilized crystals with HSA solution. In the other (direct) method, the frequency shifts were followed continuously for 60 min. while the probe was immersed in the HSA solution. An increase for the frequency shifts was observed with increasing of HSA concentration of 16-128 microg/ml. Both the immobilization and antibody-interaction conditions were found important on the extend of these specific interaction. The relations between the HSA concentrations and frequency shifts were exponential in both methods.