A single point mutation in TFIIA suppresses NC2 requirement in vivo

Negative cofactor 2 (NC2) is a dimeric histone-fold complex that represses RNA polymerase II transcription through binding to TATA-box-binding protein (TBP) and inhibition of the general transcription factors TFIIA and TFIIB. Here we study molecular mechanisms of repression by human NC2 in vivo in yeast. Yeast NC2 genes are essential and can be exchanged with human NC2. The physiologically relevant regions of NC2 have been determined and shown to match the histone-fold dimerization motif. A suppressor screen based upon limiting concentrations of NC2beta yielded a cold-sensitive mutant in the yeast TFIIA subunit Toa1. The single point mutation in Toa1 alleviates the requirement for both subunits of NC2. Biochemical characterization indicated that mutant (mt)-Toa1 dimerizes well with Toa2; it supports specific recognition of the TATA box by TBP but forms less stable TBP-TFIIA-DNA complexes. Wild-type but not the mt-Toa1 can relieve NC2 effects in purified transcription systems. These data provide evidence for a dimeric NC2 complex that is in an equilibrium with TFIIA after the initial binding of TBP to promoter TATA boxes.

The role of stromal cell-derived factor 1 on cartilage development and disease

Stromal cell-derived factor 1 (SDF-1), also known as CXC motif chemokine ligand 12 (CXCL12), is recognized as a homeostatic cytokine with strong chemotactic potency. It plays an important role in physiological and pathological processes, such as the development of multiple tissues and organs, the regulation of cell distribution, and tumour metastasis. SDF-1 has two receptors, CXC chemokine receptor type 4 (CXCR4) and CXC chemokine receptor type 7 (CXCR7). SDF-1 affects the proliferation, survival, differentiation and maturation of chondrocytes by binding to CXCR4 on chondrocytes. Therefore, SDF-1 has been used as an exogenous regulatory target in many studies to explore the mechanism of cartilage development. SDF-1 is also a potential therapeutic target for osteoarthritis (OA) and rheumatoid arthritis (RA), because of its role in pathological initiation and regulation. In addition, SDF-1 shows potent capacity in the repair of cartilage defects by recruiting endogenous stem cells in a cartilage tissue engineering context. To summarize the specific role of SDF-1 on cartilage development and disease, all articles had been screened out in PubMed by May 30, 2020. The search was limited to studies published in English. Search terms included SDF-1; CXCL12; CXCR4; chondrocyte; cartilage; OA; RA, and forty-seven papers were studied. Besides, we reviewed references in the articles we searched to get additional relevant backgrounds. The review aims to conclude the current knowledge regarding the physiological and pathological role of SDF-1 on the cartilage and chondrocyte. More investigations are required to determine methods targeted SDF-1 to cartilage development and interventions to cartilage diseases.

Independent suppression of nitric oxide and TNF alpha in the lung of conscious rats by ethanol

Tumor necrosis factor-alpha (TNF alpha) and nitric oxide (NO) mediate in part the microbicidal response of murine and rodent alveolar macrophages (AM) and recruited neutrophils (PMN) to airborne infections. Ethanol (ETOH) suppresses intrapulmonary TNF alpha and NO release and impairs pulmonary host defense mechanisms. We tested the concept that ETOH down-regulates NO by inhibiting production of TNF alpha. Male rats were given intratracheal (i.t.) saline (PBS), a polyclonal anti-TNF alpha antibody (TNFab) or nonimmune IgG (22 mg/kg, i.m.) 2 h before giving i.t. Escherichia coli endotoxin (LPS) to normal rats or rats pretreated with ETOM (5.5 g/kg, i.p.) 30 min before experimentation. AM and PMN were obtained from the bronchoalveolar lavage fluid (BAL) fluid of rats killed 2 and 4 h after administration of LPS. mRNA for inducible NO synthase (iNOS) and TNF alpha were measured in AM and PMN with competitor equalized RT-PCR techniques. The BAL fluid, AM, and PMN were assayed for TNF alpha and NO2-, and NO3- (RNI) with the L929 bioassay and chemiluminescence, respectively. TNFab abolished LPS-induced increases in TNF alpha but did not suppress the NO content of the BAL fluid or gene expression for iNOS by AM or PMN. ETOH suppressed LPS-induced increases in mRNA for iNOS, production of RNI, and BAL fluid TNF alpha but did not affect LPS-induced increases in mRNA for TNF alpha. ETOH-induced attenuation of LPS-induced up-regulation of the iNOS system did not differ in rats pretreated with TNFab or IgG. Thus, ETOH down-regulates iNOS gene expression and RNI production independent of its effects on TNF alpha. Acute ETOH administration suppresses iNOS at the level of transcription and TNF alpha at the level of translation or release of the peptide.

Nutritional enrichment of fresh apple (Royal Gala) by vacuum impregnation

This study evaluates the use of vacuum impregnation (VI) for developing nutritionally fortified fresh cut apples (Royal Gala). Cut apples were immersed in diluted high fructose corn syrup (20% w/w or 50% w/w) containing calcium or zinc. A vacuum pressure of 50 mmHg was applied for 15 min following atmospheric pressure restoration for 30 min while samples remained in the VI solution. Nutraceutical content and physicochemical properties of the apples immediately after VI were determined. Storability of VI apples at 6 degrees C and 90% relative humidity was also studied based on the color and texture of apples. Results indicated that 15-20% of the Daily Reference Intake of calcium and above 40% of the Daily Reference Intake of zinc could be obtained in 200 g fresh cut apples. VI treatments in 20% w/w high fructose corn syrup solutions had little effects on the physicochemical properties of apples. Storage study showed that VI with zinc significantly improved color stability, and calcium enhanced the firmness of the apples.

Phosphorylation-dependent block of cystic fibrosis transmembrane conductance regulator chloride channel by exogenous R domain protein

The cystic fibrosis transmembrane conductance regulator (CFTR) constitutes a linear conductance chloride channel, which is regulated by cAMP-dependent protein kinase phosphorylation at multiple sites located in the intracellular regulatory (R) domain. Studies in a lipid bilayer system, reported here, provide evidence for the control of CFTR chloride channel by its R domain. The exogenous R domain protein (encoded by exon 13 plus 85 base pairs of exon 14) interacted specifically with the CFTR molecule and inhibited the chloride conductance in a phosphorylation-dependent manner. Only the unphosphorylated R domain protein blocked the CFTR channel. Such functional interaction suggests that the putative gating particle of the CFTR chloride channel resides in the R domain.

Effect of albumin on brushite transformation to hydroxyapatite

Brushite (CaHPO(4) x 2H(2)O) is a precursor to hydroxyapatite [HA, Ca(5)(PO(4))(3)OH]. It has been shown that a modified form of brushite, with potassium substituting for calcium at specific sites, demonstrated accelerated transformation to HA when exposed to nonproteinaceous Hanks' balanced aqueous salt solutions (HBSS). The biocompatibility of a transforming material is related to cellular response to the process, which is initiated by protein adsorption. The effect of adsorbed protein on the kinetics and chemistry of brushite transformation to HA, when exposed to HBSS containing bovine serum albumin (BSA), was examined using Fourier transform IR spectroscopy, X-ray diffraction, and energy dispersive spectrometry techniques. The effect of solution pH was also studied. Results show that, in the presence of a protein-free environment, transformation is faster in buffered medium than in nonbuffered medium. Moreover, curve fitting and second derivatives of the IR spectra show that some bands shift depending on whether the brushite transforms in a buffered or nonbuffered medium. Therefore, variation in pH affects both transformation rate and the associated chemistry. The presence of BSA in either buffered or nonbuffered medium retards the transformation in comparison to the corresponding BSA-free medium. The extent of this retardation increases with the increase in bulk concentration of BSA but does not alter the transformation chemistry. This suggests the retardation on the transformation rate is due to BSA adsorption coverage on the calcium phosphate ceramic. This may be due to the shielding of Ca(2+) and PO(4)(-3) sites, preventing their interaction with the HBSS.

Rapid Determination of Rice Cultivar Responses to the Sheath Blight Pathogen Rhizoctonia solani Using a Micro-Chamber Screening Method

An accurate greenhouse screening method has not been developed previously to identify host response to sheath blight disease caused by Rhizoctonia solani Kühn that causes significant economic losses in rice yield worldwide. The unavailability of a robust screening system in the greenhouse has made it difficult to quantify disease reactions to R. solani, and has hampered studies on the genetics of resistance and plant breeding efforts to improve resistance. In an effort to develop a standardized laboratory micro-chamber screening method to quantify resistance to R. solani in rice, five rice cultivars, representing a wide range of observed disease reactions under field conditions, were examined in a blind inoculation test at three locations (Arkansas, Texas, and Colombia). Rice seedlings were inoculated at the three- to four-leaf stage with potato dextrose agar plugs containing mycelium and then covered with a 2- or 3-liter transparent plastic bottle for maintaining high humidity after inoculation. Two cultivars, Jasmine 85 and Lemont, that consistently have shown the highest and lowest levels of resistance, respectively, in previous field and greenhouse studies, were used as standards. Concurrent field experiments in Arkansas and Texas also were performed to compare the greenhouse disease ratings with those observed under field conditions. Overall, the relative disease ratings of the seven test cultivars were consistent between test locations and with field evaluations. Thus, the micro-chamber screening method can be used as an effective approach to accurately quantify resistance to the sheath blight pathogen under controlled greenhouse conditions and should help expedite the selection process to improve resistance to this important pathogen.

Bonding of composite resin to contaminated human enamel and dentin

PURPOSE

The purpose of this in vitro study was to evaluate the bond strengths of a bonding agent and composite resin system to human enamel and dentin treated with five contaminants (saliva, plasma, zinc oxide-eugenol cement, noneugenol zinc oxide cement, and handpiece lubricant) using air, moisture, and water as controls.

MATERIALS AND METHODS

A commercial bonding agent (Gluma 2000; Bayer AG, Dormagen, Germany) and its composite (Pekafill; Bayer AG) were applied to tooth structure under two conditions (contaminated and re-etched). Samples were debonded in tension after 24 hours using an inverted, truncated cone bond test.

RESULTS

Among the controls, the highest bond strengths were obtained to enamel (20 MPa) and dentin (12 MPa) with air drying. Contaminants lowered the bond strength by 20% to 100%. Re-etching without additional mechanical preparation resulted in bond strengths similar to the air control.

CONCLUSIONS

Bond strength of Gluma 2000/Pekafill to tooth structure is sensitive to common forms of contamination but can be improved by re-etching after contamination occurs.

New kelatorphan-related inhibitors of enkephalin metabolism: improved antinociceptive properties

In order to improve the in vivo protection of enkephalins from enzymatic degradation, a new series of inhibitors derived from kelatorphan [HONHCOCH2CH(CH2Ph)CONHCH(CH3)COOH], the first-described complete inhibitor of enkephalin metabolism, were designed by modification of the C-terminal amino acid. The progressive lengthening of the chain of this residue shows that a beta-alanine seems to be the best basic model for the conception of such types of compounds. On the other hand, the methylation of the amide bond, which is well accepted by aminopeptidase N (EC 3.4.11.2) and dipeptidylaminopeptidase, induced a significant loss of affinity for neutral endopeptidase -24.11. Starting from these data, compounds containing a variously substituted beta-alanine residue and corresponding to the general formula HONHCOCH2CH(CH2Ph)CONHCH(R1)CH(R2)COOH were synthesized. All these molecules inhibit neutral endopeptidase -24.11 and dipeptidylaminopeptidase in the nanomolar range, and those containing an aromatic chain (compound 7A, R1 = CH2Ph,R2 = H, and compound 8A, R1 = Ph, R2 = H) inhibit the biologically relevant aminopeptidase N, with IC50's around 10(-8) M. Intracerebroventricular injection in mice of these multienzyme inhibitors produced an efficient and naloxone-reversible analgesic response (hot plate test): compounds 7A and 8A were shown to be more potent than kelatorphan in increasing the jump latency time, in agreement with their in vitro properties, and these new compounds were found to increase the forepaw lick latency, a reflex considered as a typical morphine response.

The NC2 repressor is dispensable in yeast mutated for the Sin4p component of the holoenzyme and plays roles similar to Mot1p in vivo

NC2 (Dr1/DRAP1) and Mot1p are global repressors of transcription that have been isolated in both Saccharomyces cerevisiae and humans. NC2 is a dimeric histone-fold complex that represses RNA polymerase II transcription through binding to TBP and inhibition of TFIIA and TFIIB. Mot1p is an ATPase that removes DNA-bound TBP upon ATP hydrolysis. In this work, we studied the core promoter specificity of NC2 in vivo using a strain that carries mutated NC2beta activity. We show that NC2, like Mot1p, is required for transcription of the HIS3 and HIS4 TATA-less core promoters. Furthermore, whereas neither Mot1p nor NC2 appear to function as repressors of the HIS3 gene in cells growing exponentially in glucose, we find that both are required for repression of the HIS3 TATA promoter when cells go through the diauxic shift. Thus, the activity of these factors is similarly regulated depending upon the physiological conditions, and it appears that core promoters activated or repressed by them in vivo might be distinguishable by whether or not they contain a canonical TATA sequence. Finally, although NC2 is an essential factor for yeast viability, we isolated a mutation in a non-essential component of the holoenzyme, Sin4p, that bypasses the requirement for NC2.

Constitutive lysosomal targeting and degradation of bovine endothelin-converting enzyme-1a mediated by novel signals in its alternatively spliced cytoplasmic tail

Endothelin-converting enzyme-1 (ECE-1) is a type II membrane protein that catalyzes the proteolytic activation of big endothelin-1 to endothelin-1 (ET-1). The subcellular distribution of ECE-1, and hence the exact site of physiological activation of big ET-1, remains controversial. Here, we demonstrate with several complementary methods that the two alternatively spliced bovine ECE-1 isoforms, ECE-1a and ECE-1b, differing only in the first 30 amino acids of their N-terminal cytoplasmic tails, exhibit strikingly distinct intracellular sorting patterns. Bovine ECE-1a, which is responsible for the intracellular cleavage of big ET-1 in endothelial cells, is constitutively recruited into the lysosome, where it is rapidly degraded. In contrast, bovine ECE-1b, the isoform found in cultured smooth muscle cells, is transported to the plasma membrane by a default pathway and functions as an ectoenzyme. Mutational analyses reveal that the N-terminal tip of the cytoplasmic domain of bovine ECE-1a contains novel proline-containing signals that mediate constitutive lysosomal targeting. Analyses of chimeric ECE-1/transferrin receptors demonstrate that the cytoplasmic tail of bovine ECE-1a is sufficient for the lysosomal delivery and rapid degradation. Our results suggest that the distinct intracellular targeting of bovine ECE-1 isoforms may provide new insights into functional aspect of the endothelin system and that the cell permeability of ECE inhibitor compounds should be carefully considered during their pharmacological development.

Effect of bilateral subthalamic nucleus stimulation on parkinsonian gait

Clinical reports show that bilateral subthalamic nucleus (STN) stimulation is effective in improving parkinsonian gait. Quantitative analysis of the efficacy of STN stimulation on gait is of interest and can be carried out using a commercially available stride analyser. Ten parkinsonian patients (5 men, 5 women) with a mean age of 55.8, SD 9.6 years were included in our study. They had a mean duration of Parkinson's disease (PD) of 13.3, SD 4.5 years and a motor examination score (part III of the Unified Parkinson's Disease Rating Scale) (UPDRS) of 43, SD 13 in off-stimulation off-drug condition. All the patients had bilateral chronic STN stimulation which had started from 3 to 36 months before the study. Patients were evaluated in off-drug and on-drug conditions both with and without stimulation. We analysed the principal gait measures: velocity, cadence, stride length, gait cycle, duration of single and double limb support. The clinical parkinsonian signs were evaluated with the part III of the UPDRS. In the off-drug condition, STN stimulation significantly (p < 0.05) improved velocity and stride length. The effect was similar to that of levodopa. When STN stimulation was switched on at the best of the levodopa induced effect, no further improvement was observed. The UPDRS motor score was significantly (p < 0.001) decreased after both stimulation and levodopa. In conclusion, STN stimulation is effective on parkinsonian gait.

Synthesis of 2-(N-Acetylamino)-2-deoxy-C-glucopyranosyl nucleosides as potential inhibitors of chitin synthases

The C-glucopyranosyl nucleosides (1-4) containing the N-acetyl glucosaminyl and uridine units have been synthesized as nonhydrolyzable substrate analogues of UDP-GlcNAc aimed to inhibit the chitin synthases. The key intermediate, 4-(2'-(N-acetylamino)-3', 4',6'-tri-O-benzyl-2'-deoxy-alpha-D-glucopyranosyl)but-2-enoic acid (5), was prepared from the perbenzylated (N-acetylamino)-alpha-C-allylglucoside (7), by successive oxidative cleavage, Wittig olefination, and ester deprotection. The coupling of the acid 5 with the hydroxyl or amine function of the uridine derivatives (6a or 6b) afforded, respectively, the ester 12 and amide 14. The dihydroxylation of the conjugated double bond in ester 12 or amide 14 was better achieved with osmium tetraoxide/barium chlorate, leading to the expected diols 13 and 15 as a mixture of two diastereoisomers. The desired compounds 1-4 were obtained after catalytic hydrogenation of compounds 12-15.

Ethanol suppresses LPS-induced mRNA for nitric oxide synthase II in alveolar macrophages in vivo and in vitro

Alcohol abuse increases the incidence and severity of opportunistic lung infections and pneumonias. Inducible nitric oxide (NO) synthase (iNOS II) and NO may be a pivotal system in the intracellular bactericidal activity of macrophages. We tested the hypothesis that acute administration of ethanol (ETOH) suppressed Escherichia coli endotoxin lipopolysaccharide (LPS) mediated upregulation of the iNOS II system in the lung of the rat, in vivo. We also tested the effect of ETOH on alveolar macrophage (AM) production of free NO using microelectrodes. Male Sprague-Dawley rats were given ETOH (5.5 g/kg, IP) 30 min. before giving intratracheal sterile phosphate buffered saline solution (PBS, 0.5 ml) or LPS (1 mg/kg in a total volume of 0.5 ml PBS). The isolated lungs were subjected to bronchoalveolar lavage (BAL) 3.5 hr. later. Aliquots of the BAL fluid were assayed for tumor necrosis factor alpha TNF alpha and reactive nitrogen intermediates (nitrate and nitrite) (RNI) with chemiluminescence. Aliquots of AM were incubated 1 hr ex vivo for spontaneous production of RNI or frozen and assayed for iNOS II mRNA with competitor exchange reverse transcriptase polymerase chain reaction (cERT-PCR). The lung was homogenized and assayed for RNI. LPS increased BAL fluid TNF alpha and RNI, lung RNI, and the spontaneous production of RNI by AM, ex vivo. These effects were inhibited by in vivo administration of inhibitors of iNOS II. LPS increased iNOS mRNA in AM. This was unaffected by iNOS inhibitors. ETOH suppressed LPS-induced BAL fluid TNF, iNOS mRNA and RNI production by AM and the lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Participation of the yeast activator Abf1 in meiosis-specific expression of the HOP1 gene

The meiosis-specific gene HOP1, which encodes a component of the synaptonemal complex, is controlled through two regulatory elements, UASH and URS1H. Sites similar to URS1H have been identified in the promoter region of virtually every early meiosis-specific gene, as well as in many promoters of nonmeiotic genes, and it has been shown that the proteins that bind to this site function to regulate meiotic and nonmeiotic transcription. Sites similar to the UASH site have been found in a number of meiotic and nonmeiotic genes as well. Since it has been shown that UASH functions as an activator site in vegetative haploid cells, it seemed likely that the factors binding to this site regulate both meiotic and nonmeiotic transcription. We purified the factor binding to the UASH element of the HOP1 promoter. Sequence analysis identified the protein as Abf1 (autonomously replicating sequence-binding factor 1), a multifunctional protein involved in DNA replication, silencing, and transcriptional regulation. We show by mutational analysis of the UASH site, that positions outside of the proposed UASH consensus sequence (TNTGN[A/T]GT) are required for DNA binding in vitro and transcriptional activation in vivo. A new UASH consensus sequence derived from this mutational analysis closely matches a consensus Abf1 binding site. We also show that an Abf1 site from a nonmeiotic gene can replace the function of the UASH site in the HOP1 promoter. Taken together, these results show that Abf1 functions to regulate meiotic gene expression.

Inhibitory effect of green and black tea on tumor growth

The administration of green tea, black tea, or (-)-epigallocatechin gallate inhibited the growth of established nonmalignant and malignant tumors in tumor-bearing mice. In experiments with black tea, we found that its oral administration inhibited DNA synthesis and enhanced apoptosis in both nonmalignant and malignant tumors in tumor-bearing mice.

Protein kinase C iota protects neural cells against apoptosis induced by amyloid beta-peptide

Protein kinase C (PKC) isoforms are increasingly recognized as playing important roles in the regulation of neuronal plasticity and survival. Recent findings from studies of non-neuronal cells suggest that atypical isoforms of PKC can modulate apoptosis in various paradigms. Because increasing data support a role for neuronal apoptosis in the pathogenesis of Alzheimer's disease (AD), we tested the hypothesis that PKCiota (PKCiota) can modify vulnerability of neural cells to apoptosis induced by amyloid beta-peptide (ABP), a cytotoxic peptide linked to neuronal degeneration in AD. Overexpression of PKCiota increased the resistance of PC12 cells to apoptosis induced by ABP. Associated with the increased resistance to apoptosis were improved mitochondrial function and reduced activity of caspases. In addition, ABP-induced increases in levels of oxidative stress and intracellular calcium levels were attenuated in cells overexpressing PKCiota. These findings suggest that PKCiota prevents apoptosis induced by ABP by interrupting the cell death process at a very early step, thereby allowing the cells to maintain ion homeostasis and mitochondrial function.

Slow conversions among subconductance states of cystic fibrosis transmembrane conductance regulator chloride channel

The cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel exhibits multiple subconductance states. To study the regulation of conductance states of the CFTR channel, we expressed the wild-type CFTR protein in HEK 293 cells, and isolated microsomal membrane vesicles for reconstitution studies in lipid bilayer membranes. A single CFTR channel had a dominant conductance of 7.8 pS (H), plus two sub-open states with conductances of approximately 6 pS (M) and 2.7 pS (L) in 200 mM KCl with 1 mM MgCl2 (intracellular) and 50 mM KCl with no MgCl2 (extracellular), with pH maintained at 7.4 by 10 mM HEPES-Tris on both sides of the channel. In 200 mM KCl, both H and L states could be measured in stable single-channel recordings, whereas M could not. Spontaneous transitions between H and L were slow; it took 4.5 min for L-->H, and 3.2 min for H-->L. These slow conversions among subconductance states of the CFTR channel were affected by extracellular Mg; in the presence of millimolar Mg, the channel remained stable in the H state. Similar phenomena were also observed with endogenous CFTR channels in T84 cells. In high-salt conditions (1.5 M KCl), all three conductance states of the expressed CFTR channel, 12.1 pS, 8.2 pS, and 3.6 pS, became stable and seemed to gate independently from each other. The existence of multiple stable conductance states associated with the CFTR channel suggests two possibilities: either a single CFTR molecule can exist in multiple configurations with different conductance values, or the CFTR channel may contain multimers of the 170-kDa CFTR protein, and different conductance states are due to different aggregation states of the CFTR protein.

Extracellular matrix regulates ovarian hormone-dependent proliferation of mouse mammary epithelial cells

Mammary stromal cells can modulate steroid hormone responsiveness both in vivo and in vitro. One of the mechanisms by which stromal cells can influence epithelial cell behavior is by modifying the composition of the extracellular matrix (ECM). In this report, we have investigated the effects of five ECM molecules on control of epithelial cell proliferation by estrogen (E2) and progestin (R5020) under serum-free culture conditions. To assess the contribution of mammary gland differentiation in determining epithelial cell interactions with ECM, the behavior of mammary epithelial cells derived from nulliparous and pregnant mice was compared. We report the novel finding that the proliferative responses of mammary epithelial cells to progestin is influenced by specific ECM molecules. However, the primary determinant of hormonal responsiveness is the developmental state of the gland from which the epithelial cells were derived. Nulliparous-derived epithelial cells, proliferated in response to R5020 only on fibronectin (FN) and collagen IV (Col IV). The more highly differentiated, pregnancy-derived epithelial cells were not responsive to E2 or R5020 on any ECM. To determine if steroid hormone receptors were targets of ECM-mediated effects, ER and PR levels were analyzed. In both nulliparous and pregnancy-derived cultures, PR binding levels were maintained at similar levels on all ECMs. However, ER levels were not maintained in nulliparous-derived cultures, and this may have contributed to the lack of a significant response to E2. Alternatively or in addition, E2-induced responses may require additional signals or growth factors that are provided by stromal cells in vivo or by serum supplementation in vitro. These results demonstrate the ECM molecules, fibronectin and collagen IV, can modulate responsiveness of mammary epithelial cells to R5020 in vitro, and may be the mediators of stromal influences on hormone responsiveness in vivo. However, the specific effects of ECM and hormones are also determined by the developmental state of the mammary gland from which the cells are derived. Thus, mammary gland differentiation, ovarian hormones, and ECM composition may act in concert to determine the outcome of hormone treatment on cell proliferation.

Mitochondria and calpains mediate caspase-dependent apoptosis induced by doxycycline in HeLa cells

Doxycycline (Dc) has been demonstrated to inhibit cell growth and induce apoptosis in tumor cells, although its mechanism of action is not fully understood. The present study demonstrates that apoptosis can be induced in HeLa cells. Western blot data demonstrated that cytochrome c (Cyt c), Smac (the second mitochondria-derived activator of caspase), calpain I, caspase-9, -3 and -8 were involved in the apoptotic process, while the pan caspase inhibitor zVAD-fmk almost completely inhibited Dc-induced apoptosis. We further demonstrated that the release of mitochondrial proteins and the activation of calpains occurred upstream of the caspase cascade, in which caspase-9 was activated in response to the release of Cyt c, that caspase-8 activation was caspase and calpain dependent, and that caspase-3 was activated mainly by caspase-8 and -9. Caspase-8 played important roles in the activation of caspase-3 and induction of apoptosis, whereas the role of the caspase-9 was limited.

Transcriptional regulation of the SMK1 mitogen-activated protein kinase gene during meiotic development in Saccharomyces cerevisiae

Meiotic development (sporulation) in Saccharomyces cerevisiae is characterized by an ordered pattern of gene expression, with sporulation-specific genes classified as early, middle, mid-late, or late depending on when they are expressed. SMK1 encodes a mitogen-activated protein kinase required for spore morphogenesis that is expressed as a middle sporulation-specific gene. Here, we identify the cis-acting DNA elements that regulate SMK1 transcription and characterize the phenotypes of mutants with altered expression patterns. The SMK1 promoter contains an upstream activating sequence (UASS) that specifically interacts with the transcriptional activator Abf1p. The Abf1p-binding sites from the early HOP1 and the middle SMK1 promoters are functionally interchangeable, demonstrating that these elements do not play a direct role in their differential transcriptional timing. Timing of SMK1 expression is determined by another cis-acting DNA sequence termed MSE (for middle sporulation element). The MSE is required not only for activation of SMK1 transcription during middle sporulation but also for its repression during vegetative growth and early meiosis. In addition, the SMK1 MSE can repress vegetative expression in the context of the HOP1 promoter and convert HOP1 from an early to a middle gene. SMK1 function is not contingent on its tight transcriptional regulation as a middle sporulation-specific gene. However, promoter mutants with different quantitative defects in SMK1 transcript levels during middle sporulation show distinct sporulation phenotypes.

A peptide derived from the intercellular adhesion molecule-2 regulates the avidity of the leukocyte integrins CD11b/CD18 and CD11c/CD18

beta 2 integrin (CD11a,b,c/CD18)-mediated cell adhesion is required for many leukocyte functions. Under normal circumstances, the integrins are nonadhesive, and become adhesive for their cell surface ligands, the intercellular adhesion molecules (ICAMs), or soluble ligands such as fibrinogen and iC3b, when leukocytes are activated. Recently, we defined a peptide derived from ICAM-2, which specifically binds to purified CD11a/CD18. Furthermore, this peptide strongly induces T cell aggregation mainly mediated by CD11a/CD18-ICAM-1 interaction, and natural killer cell cytotoxicity. In the present study, we show that the same ICAM-2 peptide also avidly binds to purified CD11b/CD18, but not to CD11c/CD18. This binding can be blocked by the CD11b antibody OKM10. The peptide strongly stimulates CD11b/CD18-ICAM-1-mediated cell aggregations of the monocytic cell lines THP-1 and U937. The aggregations are energy and divalent cation-dependent. The ICAM-2 peptide also induces CD11b/CD18 and CD11c/CD18-mediated binding of THP-1 cells to fibrinogen and iC3b coated on plastic. These findings indicate that in addition to induction of CD11a/CD18-mediated cell adhesion, the ICAM-2 peptide may also serve as a "trigger" for high avidity ligand binding of other beta 2 integrins.