A gene cluster for macrolide antibiotic biosynthesis in Streptomyces venezuelae: architecture of metabolic diversity

In a survey of microbial systems capable of generating unusual metabolite structural variability, Streptomyces venezuelae ATCC 15439 is notable in its ability to produce two distinct groups of macrolide antibiotics. Methymycin and neomethymycin are derived from the 12-membered ring macrolactone 10-deoxymethynolide, whereas narbomycin and pikromycin are derived from the 14-membered ring macrolactone, narbonolide. This report describes the cloning and characterization of the biosynthetic gene cluster for these antibiotics. Central to the cluster is a polyketide synthase locus (pikA) that encodes a six-module system comprised of four multifunctional proteins, in addition to a type II thioesterase (TEII). Immediately downstream is a set of genes for desosamine biosynthesis (des) and macrolide ring hydroxylation. The study suggests that Pik TEII plays a role in forming a metabolic branch through which polyketides of different chain length are generated, and the glycosyl transferase (encoded by desVII) has the ability to catalyze glycosylation of both the 12- and 14-membered ring macrolactones. Moreover, the pikC-encoded P450 hydroxylase provides yet another layer of structural variability by introducing regiochemical diversity into the macrolide ring systems. The data support the notion that the architecture of the pik gene cluster as well as the unusual substrate specificity of particular enzymes contributes to its ability to generate four macrolide antibiotics.

Crystal structure of carbonic anhydrase from Neisseria gonorrhoeae and its complex with the inhibitor acetazolamide

The crystal structure of carbonic anhydrase from Neisseria gonorrhoeae has been solved to a resolution of 1.78 A by molecular replacement using human carbonic anhydrase II as a template. After refinement the R factor was 17.8% (Rfree=23.2%). There are two molecules per asymmetric unit (space group P21), but they have essentially identical structures. The fold of the N. gonorrhoeae enzyme is very similar to that of human isozyme II; 192 residues, 74 of which are identical in the two enzymes, have equivalent positions in the three-dimensional structures. This corresponds to 85% of the entire polypeptide chain of the bacterial enzyme. The only two cysteine residues in the bacterial enzyme, which has a periplasmic location in the cell, are connected by a disulfide bond. Most of the secondary structure elements present in human isozyme II are retained in N. gonorrhoeae carbonic anhydrase, but there are also differences, particularly in the few helical regions. Long deletions in the bacterial enzyme relative to human isozyme II have resulted in a considerable shortening of three surface loops. One of these deletions, corresponding to residues 128 to 139 in the human enzyme, leads to a widening of the entrance to the hydrophobic part of the active site cavity. Practically all the amino acid residues in the active site of human isozyme II are conserved in the N. gonorrhoeae enzyme and have similar structural positions. However, the imidazole ring of a histidine residue, which has been shown to function as a proton shuttle in the catalytic mechanism of the human enzyme, interacts with an extraneous entity, which has tentatively been identified as a 2-mercaptoethanol molecule from the crystallization medium. When this entity is removed by soaking the crystal in a different medium, the side-chain of His66 becomes quite mobile. The structure of a complex with the sulfonamide inhibitor, acetazolamide, has also been determined. Its position in the active site is very similar to that observed in human carbonic anhydrase II.

Crystal structure of spinach plastocyanin at 1.7 A resolution

The crystal structure of plastocyanin from spinach has been determined using molecular replacement, with the structure of plastocyanin from poplar as a search model. Successful crystallization was facilitated by site-directed mutagenesis in which residue Gly8 was substituted with Asp. The region around residue 8 was believed to be too mobile for the wild-type protein to form crystals despite extensive screening. The current structure represents the oxidized plastocyanin, copper (II), at low pH (approximately 4.4). In contrast to the similarity in the core region as compared to its poplar counterpart, the structure shows some significant differences in loop regions. The most notable is the large shift of the 59-61 loop where the largest shift is 3.0 A for the C(alpha) atom of Glu59. This results in different patterns of electrostatic potential around the acidic patches for the two proteins.

Cell kinetics of prostate exocrine and neuroendocrine epithelium and their differential interrelationship: new perspectives

The prostate gland consists of a complex ductal system lined with exocrine basal and luminal cells, and neuroendocrine epithelial cells. This paper reviews the histologic and molecular cell biologic characteristics of these cells, in normal adult tissue, during prostate morphogenesis, and in the development of benign and malignant neoplastic conditions. Expression of differentiation markers, as well as proliferation and apoptosis markers, growth factors and associated receptors, and abnormalities in genes and chromosomes are reviewed. Accumulating data indicate that (1) pluripotent immortal stem cells are located in the basal cell compartment of the prostate; (2) there is a subpopulation of epithelial cells in the prostate gland (intermediate cells) that have both structural and functional characteristics common to basal and luminal cells, which may be identified in various conditions; and prostate NE cells may have the same common origin as other exocrine cells, and share the same differentiation pathway. A stem cell model is proposed in which both exocrine and endocrine cells are derived from a subpopulation of basal cells (stem cell) that give rise to luminal cells through intermediate cells (pluripotent amplifying cells). These cells are also probably highly implicated in the early development of prostate benign and malignant neoplasia.

A case of acute megakaryocytic leukemia presenting as peripheral acute leukemia with complex karyotypic abnormalities

Peripheral acute leukemia (PAL) is extremely rare. We report on the first case of acute megakaryocytic leukemia presenting with PAL and complex chromosomal abnormalities. At diagnosis, the patient had 10.5-21% marrow blasts and 55-60% peripheral blasts which expressed CD42b and CD61. Two related clones with the karyotype of 48,X,-X,+3,+9,del(9)(q12q31) x 2,+17,i(17)(q10)/ 49,idem, +18 were revealed by conventional cytogenetics, but no AML-1/ETO fusion transcript was detected by RT-PCR assay. The significance of this case is discussed concisely.

[Effect of qingjieling induced endogenous granulocyte-colony stimulating factor in strengthening host defence against bacteria]

OBJECTIVE

To explore the effect of Qingjieling (QJL) induced endogenous granulocyte-colony stimulating factor (G-CSF) in strengthening host defence against bacteria in mice.

METHODS

Serum containing G-CSF was obtained by injecting 5 mg/g of QJL to mice. The CSF activity was identified by ELISA, bone marrow cell proliferation and colony-forming assays. Forty-eight hours after the serum was infused to 8 normal BALB/C mice, the mice was sacrificed and the number of E. coli in spleen suspension was measured. Eight mice of the control group were treated in the same way but with normal serum of mice instead of the QJL treated serum.

RESULTS

The QJL treated serum showed a positive reaction with anti-G-CSF McAb, it promoted the proliferation of bone marrow cells and formation of cell colony of neutrophilic granulocyte type in the culture medium, these results indicated that the serum contained G-CSF undoubtedly. The number of E. coli in spleen suspension of test group was significantly lower than that of the control group P < 0.01).

CONCLUSIONS

QJL does enhance the defense capability of the host, the mechanism of which partly might be due to the induction of endogenous G-CSF in the host.

MS-551 and KCB-328, two class III drugs aggravated adrenaline-induced arrhythmias

We investigated the proarrhythmic effects of MS-551 and KCB-328, class III antiarrhythmic drugs using adrenaline-induced arrhythmia models in halothane anaesthetized, closed-chest dogs. In the control period, adrenaline, starting from a low dose of 0.25 to up to 1.0 microg/kg/50 s i.v., was injected to determine the arrhythmia inducing dose and the non-inducing dose. After MS-551 or KCB-328 administration, the adrenaline injection was repeated and the interval between the injection and the occurrence of arrhythmia (latent interval), the changes in arrhythmic ratio (as calculated by dividing the number of ventricular premature contraction by the number of the total heart rate) and the severity of arrhythmia were observed. MS-551 infusion, 1 mg/kg/30 min, decreased the heart rate (HR) by 16% (P<0.01) and prolonged the QTc interval by 20% (P<0.01). During the 30 min of MS-551 infusion, arrhythmias occurred in three out of seven dogs (torsades de pointes (TdP) type VT in one dog). After these arrhythmias disappeared, MS-551 decreased the latent interval of the adrenaline arrhythmias produced by the inducing dose (30+/-2 s compared with 43+/-3 s of the control interval, P < 0.05), increased the arrhythmic ratio (P<0.05) and induced arrhythmias by non-inducing adrenaline doses (P<0.05). Effect of a new class III drug KCB-328 infusion, 0.3 mg/kg/30 min, was compared witih MS-551 using the same model. KCB-328 decreased the HR by 21% (P<0.01) and prolonged the QTc interval by 25% (P<0.01). During the 30 min of infusion, arrhythmias occurred in five out of seven dogs (TdP in two dogs). KCB-328 also decreased the latent interval of the adrenaline arrhythmias produced by the inducing doses (31+/-3 s compared with 49+/-7 s of the control period, P<0.05), but did not significantly alter the arrhythmic ratio. Adrenaline induced TdP only after MS-551 or KCB-328 was administered, i.e. after MS-551, 1 mg/kg/30 min, 3/7 versus 0/7 in the control; KCB, 0.3 mg/kg/30 min, 3/7 versus 0/7 in the control. To examine the direct arrhythmogenic effect of MS-551 and whether an adrenergic mechanism plays some role on this arrhythmogenesis, a bolus injection of MS-551, 3 mg/kg, was injected either without pre-treatment or after pre-treatment with propranolol 0.3 mg/kg. MS-551 induced arrhythmias in five out of seven dogs (TdP in one dog). Also in the propranolol pre-treated dogs, MS-551 induced arrhythmias in five out of seven dogs (TdP in 1 dog). In conclusion, these observations indicate that MS-551 and KCB-328 induced arrhythmias and intensified proarrhythmic effects of adrenaline, MS-551 being stronger than KCB-328 at the same QTc prolonging doses. The direct arrhythmogenic effect of MS-551 was not influenced by beta-blocker treatment.

Antiarrhythmic effects of a novel class III drug, KCB-328, on canine ventricular arrhythmia models

KCB-328 is a newly synthesized class III drug. To determine whether this drug has antiarrhythmic or proarrhythmic effects, we used canine ventricular arrhythmia models induced by coronary ligation and reperfusion, programmed electrical stimulation (PES), two-stage coronary ligation, digitalis, or epinephrine. KCB-328, in an intravenous infusion of 0.5 mg/kg/30 min, prolonged the QTc interval only 11%, but had antiarrhythmic effects on the reentry arrhythmias induced by PES (12 of 12 dogs with old myocardial infarction; p < 0.05). KCB-328, in an infusion of 1 mg/kg/h, suppressed the occurrence of fatal ventricular fibrillation (VF) induced by coronary ligation and reperfusion under either halothane anesthesia (p < 0.05) or pentobarbital anesthesia (p < 0.05). Under the halothane anesthesia, KCB-328 alone showed proarrhythmic effects [i.e., induction of ventricular premature contractions (VPCs)], but it did not induce a more severe effect such as torsades de pointes-type ventricular tachycardia (VT). In addition, KCB-328 had weak antiarrhythmic effects on the automaticity arrhythmias induced by 24-h coronary ligation but was effective neither on 48-h coronary ligation arrhythmias nor on the digitalis- and epinephrine-induced arrhythmias. Our results indicate that KCB-328 has powerful antiarrhythmic effects with fewer proarrhythmic potencies.

Tenascin-C expression in prostatic intraepithelial neoplasia (PIN): a marker of progression?

BACKGROUND

Tenascin (tenascin-C) has been suggested to be associated with active epithelial-stromal interactions. We evaluated tenascin expression in tissue remodelling processes presumably associated with PIN and prostate carcinoma (PCa).

MATERIALS AND METHODS

Tenascin immunoreactivity was evaluated in 38 PIN lesions (low-grade = 5, high-grade = 33) from 27 paraffin-embedded PCa specimens, and compared with expression in pre-existent (normal) prostate, benign prostatic hyperplasia (BPH), and PCa.

RESULTS

Periepithelial stromal tenascin expression was low in low-grade PIN, and similar to normal glands and BPH, whereas expression in high-grade PIN was high and partly overlapped that of well-/moderately differentiated PCa. High-grade PCa usually expressed little, if any tenascin.

CONCLUSIONS

The variable periglandular tenascin expression in high-grade PIN may reflect the biologic behaviour of this lesion, and may be indicative of variable levels of tissue remodelling. In well/moderately differentiated PCa tenascin expression levels may be an indicator of tumour progression.

High-level expression and purification of human pro-UK cDNA in Escherichia coli

A chemically synthesized human pro-urokinase (pro-UK) CDNA was cloned into the expression vector PET-11d and expressed in E. coli BL21(DE3) pLysS under the control of the T7 promoter. Using 0.1 mmol/L IPTG induction, the expression level of the recombinant pro-UK attained up to 15% of the total bacterial proteins and existed as inclusion bodies. After denaturation and renaturation in vitro, the expressed pro-UK was purified to be identified by Zn2+ selective precipitation, immuno-affinity chromatography, and benzamidine affinity adsorption. The specific activity of the purified human pro-UK was about 110,000 IU/mg.

Expression of periglandular tenascin-C and basement membrane laminin in normal prostate, benign prostatic hyperplasia and prostate carcinoma

OBJECTIVE

To evaluate the structural relationship of the distribution between tenascin (tenascin-C, an extra-cellular matrix glycoprotein involved in stromal-epithelial interactions in both normal and pathological conditions) and laminin, an important component of the basement membrane, in normal and neoplastic human prostate, and to establish whether changes in the basement membrane are accompanied by changes in tenascin staining.

MATERIALS AND METHODS

Seventy-five snap-frozen prostate samples representing normal glands, nodular benign prostatic hyperplasia and prostate carcinoma were stained for tenascin. From these, 15 samples were selected for dual-immunofluorescence staining and a confocal laser scan microscope was used to simultaneously visualize tenascin and laminin immunoreactivity.

RESULTS

Tenascin was expressed in the extracellular matrix, mainly at the periphery of the glands, in tumour foci and blood vessels. In cases with intact basement membranes, e.g. normal glands and hyperplastic lesions, tenascin expression was weak. Low- and moderate-grade tumours were characterized by strong tenascin expression, while laminin expression was weak and/or showed discontinuities, indicating disturbances in basement membrane composition. High-grade tumours had sparse tenascin staining and a marked loss of laminin immunoreactivity.

CONCLUSION

These results indicate that periglandular tenascin expression correlates with the integrity of the basement membrane in the human prostate. By influencing stromal-epithelial interactions, tenascin may play a role in maintaining tissue homeostasis in the prostate.

Interfering with the inhibitory mechanism of serpins: crystal structure of a complex formed between cleaved plasminogen activator inhibitor type 1 and a reactive-centre loop peptide

BACKGROUND

Plasminogen activator inhibitor type 1 (PAI-1) is an important endogenous regulator of the fibrinolytic system. Reduction of PAI-1 activity has been shown to enhance dissolution of blood clots. Like other serpins, PAI-1 binds covalently to a target serine protease, thereby irreversibly inactivating the enzyme. During this process the exposed reactive-centre loop of PAI-1 is believed to undergo a conformational change becoming inserted into beta sheet A of the serpin. Incubation with peptides from the reactive-centre loop transform serpins into a substrate for their target protease. It has been hypothesised that these peptides bind to beta sheet A, thereby hindering the conformational rearrangement leading to loop insertion and formation of the stable serpin-protease complex.

RESULTS

We report here the 1.95 A X-ray crystal structure of a complex of a glycosylated mutant of PAI-1, PAI-1-ala335Glu, with two molecules of the inhibitory reactive-centre loop peptide N-Ac-TVASS-NH2. Both bound peptide molecules are located between beta strands 3A and 5A of the serpin. The binding kinetics of the peptide inhibitor to immobilised PAI-1-Ala335Glu, as monitored by surface plasmon resonance, is consistent with there being two different binding sites.

CONCLUSIONS

This is the first reported crystal structure of a complex formed between a serpin and a serpin inhibitor. The localisation of the inhibitory peptide in the complex strongly supports the theory that molecules binding in the space between beta strands 3A and 5A of a serpin are able to prevent insertion of the reactive-centre loop into beta sheet A, thereby abolishing the ability of the serpin to irreversibly inactivate its target enzyme. The characterisation of the two binding sites for the peptide inhibitor provides a solid foundation for computer-aided design of novel, low molecular weight PAI-1 inhibitors.

Identification of the ice-binding surface on a type III antifreeze protein with a "flatness function" algorithm

Antifreeze proteins (AFPs) adsorb to surfaces of growing ice crystals, thereby arresting their growth. The prevailing hypothesis explains the nature of adsorption in terms of a match between the hydrophilic side chains on the AFP's ice-binding surface (IBS) and the water molecules on the ice surface. The number and spatial arrangement of hydrogen bonds thus formed have been proposed to account, respectively, for the binding affinity and specificity. The crystal structure of a type III AFP from ocean pout (isoform HPLC-3) has been determined to 2.0-A resolution. The structure reveals an internal dyad motif formed by two 19-residue, loop-shaped elements. Based on of the flatness observed on the type I alpha-helical AFP's IBS, an automated algorithm was developed to analyze the surface planarity of the globular type III AFP and was used to identify the IBS on this protein. The surface with the highest flatness score is formed by one loop of the dyad motif and is identical to the IBS deduced from earlier mutagenesis studies. Interestingly, 67% of this surface contains nonpolar solvent-accessible surface area. The success of our approach to identifying the IBS on an AFP, without considering the presence of polar side chains, indicates that flatness is the first approximation of an IBS. We further propose that the specificity of interactions between an IBS and a particular ice-crystallographic plane arises from surface complementarity.

[Cytogenetic analysis of 600 cases with chronic myelogenous leukemia]

OBJECTIVE

This was a retrospective analysis of cytogenetic data from 600 cases with chronic myelogenous leukemia (CML) to investigate the features of Ph chromosome and its significance.

METHODS

Bone marrow direct method and/or short-term culture were used to prepare the chromosomes and karyotype analysis was performed with R-banding technique.

RESULTS

30 cases (5%) were Ph negative; 570 cases (95%) were Ph positive. 535 cases (93.8%) had standard Ph translocation;34 cases(5.9%) had variant translocation, including 13 cases (2.2%) with simple variant translocation, 13 cases (2.2%) with complex variant translocation and 8 cases (1.4%) with masked Ph chromosome. 526 cases (92.2%) had 100% of Ph positive cells; 44 cases (7.7%) had normal karyotype in partial or all metaphases after treatment such as allogeneic bone marrow transplantation, interferon and pulse hydroxyurea therapy, but conventional chemotherapy had no effect on the percentage of Ph positive cells. 50.6% of Ph positive CML with blast crisis had extra chromosomal abnormalities, of which, the most common ones were +8(46.1%),2 Ph(33.9%) and i(17q) (23%) in descending order.

CONCLUSION

These facts indicate that chromosome examinations not only help diagnose and differentiate CML,but also help predict the blast crisis, evaluate the therapeutic effect, and make a cytogenetic classification for CML.

Maleylated-BSA enhances production of nitric oxide from macrophages

Maleylated-bovine serum albumin (maleyl-BSA) elicits transcription and secretion of a number of proinflammatory genes via ligation of the low-affinity scavenger receptor (SR) on macrophages. We now demonstrate that while neither maleyl-BSA, nor interferon-gamma (INF-gamma) alone induce nitric oxide (NO) production, when combined they promote release of NO from murine peritoneal macrophages. This effect was blocked by treatment with oxidized-low density lipoprotein. Maleyl-BSA activated NF-kappaB dimers capable of binding the NF-kappaBd sequence unique to the iNOS promoter, but this failed to induce significant new transcription or accumulation of iNOS mRNA. The combination of maleyl-BSA and IFN-gamma failed to demonstrate synergy at the transcriptional or mRNA levels, as these levels were comparable to those elicited by IFN-gamma alone. These studies suggest that the synergy in NO production between maleyl-BSA and IFN-gamma occurs after the accumulation of iNOS-specific mRNA, possibly at the translational or post-translational level.

Diversity of HIV-1 Vpr interactions involves usage of the WXXF motif of host cell proteins

Targeting protein or RNA moieties to specific cellular compartments may enhance their desired functions and specificities. Human immunodeficiency virus type I (HIV-1) encodes proteins in addition to Gag, Pol, and Env that are packaged into virus particles. One such retroviral-incorporated protein is Vpr, which is present in all primate lentiviruses. Vpr has been implicated in different roles within the HIV-1 life cycle. In testing a new hypothesis in which viral proteins are utilized as docking sites to incorporate protein moieties into virions, we used the peptide phage display approach to search for Vpr-specific binding peptides. In the present studies, we demonstrate that most of the peptides that bind to Vpr have a common motif, WXXF. More importantly, we demonstrate that the WXXF motif of uracil DNA glycosylase is implicated in the interaction of uracil DNA glycosylase with Vpr intracellularly. Finally, a dimer of the WXXF motif was fused to the chloramphenicol acetyl transferase (CAT) gene, and it was demonstrated that the WXXF dimer-CAT fusion protein construct produces CAT activity within virions in the presence of Vpr as a docking protein. This study provides a novel potential strategy in the targeting of anti-viral agents to interfere with HIV-1 replication.

GPR1 encodes a putative G protein-coupled receptor that associates with the Gpa2p Galpha subunit and functions in a Ras-independent pathway

The yeast RAS1 and RAS2 genes appear to be involved in control of cell growth in response to nutrients. Here we show that this growth control also involves a signal mediated by the heterotrimeric G protein alpha subunit homolog encoded by GPA2. A GPA2 null allele conferred a severe growth defect on cells containing a null allele of RAS2, although either mutation alone had little effect on growth rate. A constitutive allele of GPA2 could stimulate growth of a strain lacking both RAS genes. Constitutive GPA2 conferred heat shock sensitivity on both wild-type cells and cells lacking RAS function, but had no effect in a strain containing a null allele of SCH9, which encodes a kinase related to protein kinase A. The GPR1 gene was isolated and was found to encode a protein with the characteristics of a G protein-coupled receptor. Double Deltagpr1 Deltaras2 mutants displayed a severe growth defect that was suppressed by expression of the constitutive allele of GPA2, confirming that GPR1 acts upstream of GPA2. Gpr1p is expressed on the cell surface and requires sequences in the membrane-proximal region of its third cytoplasmic loop for function, as expected for a G protein-coupled receptor. GPR1 RNA was induced when cells were starved for nitrogen and amino acids. These results are consistent with a model in which the GPR1/GPA2 pathway activates the Sch9p kinase to generate a response that acts in parallel with that generated by the Ras/cAMP pathway, resulting in the integration of nutrient signals.

Identification of intermediate cell types by keratin expression in the developing human prostate

BACKGROUND

The secretory acini of the adult human prostate contain basal, luminal, and intermediate types of exocrine cells. Intermediate cells are thought to play an important role in normal growth and neoplastic transformation. In this study we investigated whether this cell type is present in early stages of prostate development, using keratin antibodies specific for them.

METHODS

Autoptic tissue from 11 prepubertal and 5 normal adult prostates was immunohistochemically stained with four keratin antibodies capable of specifically detecting basal, luminal, or intermediate cell types.

RESULTS

Morphologically, in fetal prostate cells differentiation was often not evident. However, basally located cells usually displayed a basal-cell keratin-phenotype. Morphologically similar cells with more luminal localization expressed keratins typical of luminal cells, or of intermediate cells.

CONCLUSIONS

1) In early stages of prostate development, cells with intermediate keratin-phenotype can be identified. 2) Their large numbers comply with a hierarchical pathway of cellular differentiation from basal to luminal cells. 3) The presence of intermediate cells at such an early fetal age may reflect their regulatory function in prostate development.

[Study on combined chemosensitivity test in acute non-lymphocytic leukemia]

OBJECTIVE

To explore the methods of combined chemosensitivity test in vitro.

METHODS

The chemosensitivity of leukemia cells to 7 kinds of combined chemotherapy regimens, including DA, HA, AA, MA, HAD, HAA and HAM, was estimated in 79 patients with ANLL by MTT assay in vitro. The ratios of drug combinations at which synergistic interactions between drugs are to the highest levels were determined by using Chou's "median effect analysis".

RESULTS

There were 67 S(sensitive)/S, 9 R(resistant)/R, 2 R/S, 1 S/R(in vitro/in vivo) in 79 patients. The general, positive and negative coincident rates of in vitro with in vivo, specificity and sensitivity were 96.2%, 98.5%, 81.8%, 88.9% and 97.1%, respectively.

CONCLUSION

This method is better than the single drug test, and it is more useful to find drug resistant patients.

[Strain of screening high toxin--producing from Corynebacterium diphtheria PW8-weissensee]

Corynebacterium diphtheria PW8-weissensee was grown on different media for screening high toxin produce. Through six times of screening (selecting butyrous brilliant smooth small colonies and testing their toxin production capacity) from original strain producing toxin 160 Lf/ml, a high toxin--producing descendand culture was obtained, which produced 79% more toxin than the original strain did.

Architectural DNA binding by a high-mobility-group/kinesin-like subunit in mammalian SWI/SNF-related complexes

The SWI/SNF complex in yeast and Drosophila is thought to facilitate transcriptional activation of specific genes by antagonizing chromatin-mediated transcriptional repression. The mechanism by which it is targeted to specific genes is poorly understood and may involve direct DNA binding and/or interactions with specific or general transcription factors. We have previously purified a mammalian complex by using antibodies against BRG1, a human homologue of SWI2/SNF2. This complex is likely functionally related to the yeast SWI/SNF complex because all five subunit identified so far (referred to as BAFs, for BRG1-associated factors) are homologues of the yeast SWI/SNF subunits. However, we now describe the cloning of the 57-kDa subunit (BAF57), which is present only in higher eukaryotes but not in yeast. BAF57 is shared by all mammalian complexes and contains a high-mobility-group (HMG) domain adjacent to a kinesin-like region. Both recombinant BAF57 and the whole complex bind four-way junction (4WJ) DNA, which is thought to mimic the topology of DNA as it enters or exits the nucleosome. Surprisingly, complexes with mutations in the HMG domain of BAF57 can still bind 4WJ DNA and mediate ATP-dependent nucleosome disruption. Our work describes the first DNA binding subunit for SWI/SNF-like complexes and suggest that the mechanism by which mammalian and Drosophila SWI/SNF-like complexes interact with chromatin may involve recognition of higher-order chromatin structure by two or more DNA binding domains.

Prostatic neuroendocrine cells have a unique keratin expression pattern and do not express Bcl-2: cell kinetic features of neuroendocrine cells in the human prostate

We investigated the keratin phenotype and bcl-2 immunoreactivity of neuroendocrine cells in the human prostate to determine whether the postmitotic status of these cells is associated with protection from apoptosis by bcl-2 protein expression and to elucidate the possible cell kinetic relationship between neuroendocrine cells and the other epithelial components of the prostate. Tissue specimens were selected from prostates of 19 patients harboring normal secretory glands (n = 15) and glandular benign prostatic hyperplasia (n = 10). Using a novel sequentially selective destaining immunoenzymatic cytochemical technique we were able to demonstrate the distribution of neuroendocrine cells, keratin markers identifying either basal, luminal, or intermediate cells, and the bcl-2 protein in single sections. Basal cell keratins were expressed in the minority of the neuroendocrine cells. In most of the cells, intermediate and luminal cell keratins were found and bcl-2 was constantly negative. Our findings indicate that neuroendocrine cells and other epithelial cells in the human prostate share a common keratin phenotype and probably originate from a common epithelial precursor. From the absence of bcl-2 we infer that the neuroendocrine cells have no progenitor cell characteristics.

[Preliminary study on method for predicting lower body negative pressure tolerance]

To find out a method to predict lower body negative pressure (LBNP) tolerance with noninvasive physiological measurements, 11 healthy young subjects were tested in an LBNP chamber in sitting position. Incremental negative pressure was used for evaluating LBNP tolerance time. End points of the test were onset of presyncopal symptoms or completion of 15 min test. According to their reactions, the 11 subjects were divided into good tolerance group (group A, n = 5) and poor tolerance group (group B, n = 6); At the 11th minute of LBNP, mean arterial pressure (MAP), magnitude of decrease of regional cerebral oxygen saturation (delta SrO2) and cardiac output (delta CO) showed significant difference between group A and B(P <0.05); Mean error was 0.54 +/- 0.42 min when LBNP tolerance was predicted using MAP and delta SrO2 at this moment by regression analysis.