Characterization of a non-glycosylated fraction from honey proteins of Melipona beecheii with antimicrobial activity against Escherichia coli O157:H7.

AIMS: To analyse the non-glycosylated protein fraction from Melipona beecheii honey for antimicrobial activity against Escherichia coli O157:H7. METHODS AND RESULTS: The proteins from M. beecheii honey were separated according to their degree of glycosylation using Concanavalin A-affinity chromatography. The total protein extract and its fractions were analysed by 1D and 2D electrophoresis. We also determined the antimicrobial and antihaemolytic activities of the total protein extract and the non-glycosylated fraction. Furthermore, we evaluated the effect of this non-glycosylated fraction for the expression of the Stx1, Stx2, EAE and HlyA pathogen genes. Melipona beecheii honey contained at least 24 proteins with molecular weights ranging between 7·6 and 95 kDa and isoelectric points between 3 and 10, three proteins from the 24 are non-glycosylated. The non-glycosylated fraction had an MIC90 of 1·128 µg ml-1 , and this fraction inhibited the haemolytic activity of the pathogen, as well as reduced the expression of Stx1, Stx2 and HlyA. The MbF1-2 protein from the non-glycosylated fraction was sequenced and identified as a homologue of the royal jelly-like protein of Melipona quadrifasciata. CONCLUSIONS: The non-glycosylated protein fraction from M. beecheii honey greatly contributes to antibacterial activity and it is composed of at least three proteins, of which MbF1-2 provided over 50% of the antimicrobial activity. SIGNIFICANCE AND IMPACT OF THE STUDY: The study showed significant antimicrobial activity from several proteins present in the honey of M. beecheii. Interestingly, the non-glycosylated protein fraction demonstrated antihaemolytic activity and adversely affected the expression of virulence genes in Escherichia coli O157:H7; these proteins have the potential to be used in developing therapeutic agents against this bacterium.

Human papillomavirus 16/18 infections in lung cancer patients in Mexico.

BACKGROUND/AIMS: Human papillomavirus (HPV) is an epitheliotropic, double-stranded DNA virus, and its high-risk genotypes are associated with human cancer. HPV genome has been detected in lung carcinomas in certain places around the world, including Mexico; however, the prevalence of this is unclear. In this study, we examine the frequency of high-risk HPV 16/18 in lung cancer tissues from a Mexican population. METHODS: 39 lung cancer specimens were analyzed by polymerase chain reaction (PCR) using HPV GP5+/GP6+ primers and then were genotyped using specific primers to HPV 16/18. Additionally, in situ hybridization (ISH) was performed using BIO-labeled oligonucleotide probes. RESULTS: Our results identified 15 positive cases (38.46%) for HPV 16 and 1 positive case (2.56%) for HPV 18 by PCR. ISH showed the presence of HPV DNA in 13 of 16 (81%) samples, in agreement with the PCR results. CONCLUSIONS: In this study, we detected HPV 16/18 gene sequences in lung cancer samples obtained from Mexican patients by PCR and ISH. We found the highest prevalence of HPV 16 infection in lung adenocarcinomas, suggesting that HPV infection may be associated with lung cancer. However, further studies are needed to elucidate the role of HPV in lung carcinogenesis.

Olfactomedin-like 3 (OLFML3) gene expression in baboon and human ocular tissues: cornea, lens, uvea, and retina.

BACKGROUND: Olfactomedin-like is a family of polyfunctional polymeric glycoproteins. This family has at least four members. One member of this family is OLFML3, which is preferentially expressed in placenta but is also detected in other adult tissues including the liver and heart. However, its orthologous rat gene is expressed in the iris, sclera, trabecular meshwork, retina, and optic nerve. METHODS: OLFML3 messenger amplification was performed by RT-PCR from human and baboon ocular tissues. The products were cloned and sequenced. RESULTS: We report OLFML3 expression in human and baboon eye. The full coding DNA sequence has 1221 bp, from which an open reading frame of 406 amino acid was obtained. The baboon OLFML3 gene nucleotidic sequence has 98% and amino acidic 99% similarity with humans. CONCLUSIONS: OLFML3 gene expression in human and baboon ocular tissues and its high similarity make the baboon a powerful model to deduce the physiological and/or metabolic function of this protein in the eye.

WT1 gene silencing by aerosol delivery of PEI-RNAi complexes inhibits B16-F10 lung metastases growth.

The Wilms' tumor gene 1 (WT1) is a universal tumor antigen and consequently a good therapeutic target for the development of gene therapy strategies. Earlier, we reported the in vitro efficacy of WT1 RNAi in the inhibition of B16F10 murine melanoma cell line growth. In this study, we used an aerosol system to deliver WT1 RNAi complexes, polyethyleneimine (PEI)-WT1-1 or PEI-WT1-2, to the lungs of mice with B16F10 lung metastasis. This treatment produced a statistically significant (P=0.020) reduction in the number and size of lung tumor foci, resulting in decreased lung weight and tumor index in treated mice compared with controls. The WT1 RNAi treatment also reduced the number and size of tumor blood vessels, suggesting decreased angiogenesis. Furthermore, the treated lung tissue showed cells in the tumor infiltrations undergoing apoptosis and elevated expression of the proapoptotic genes Bcl-xS and Bax, suggesting an activation of the intrinsic apoptotic pathway. Overall, WT1-1 treatment prolonged the mean survival time of tumor-bearing mice in comparison with the control and WT1-2-treated mice. Our data show that WT1 gene silencing in vivo by aerosol delivery of PEI-WT1 RNAi complexes is an effective therapeutic strategy for the treatment of lung metastases.

Entamoeba histolytica: cyst-like structures in vitro induction.

The cyst of Entamoeba histolytica is responsible for amebiasis infection. However, no axenic in vitro system exists that promotes mass encystation for studying this process of this human-infecting parasite. Cyst-like structures of E. histolytica obtained in this work were induced using TYI-S-33 media in combination with enterobacterias Escherichia coli and Enterococcus faecalis conditioned media, high CO2 tension and histamine. Cyst-like structures showed the same characteristics of a typical E. histolytica cyst: aggregation, resistance to 0.15% sarcosyl for 10 min, high signal of fluorescence under UV light when stained with 10% calcofluor M2r and the surface topology showed a wrinkled wall. In addition these structures are multinucleated with condensed chromatin attached to nuclear membrane, contain big vacuoles and ribonucleoproteic helices in the cytoplasm and also present a thin cell wall. Last all characteristics are all the same as a typical of E. histolytica cyst.

Functional domains of human growth hormone necessary for the adipogenic activity of hGH/hPL chimeric molecules.

Genetic analysis through construction of chimeric genes and their transfection in mammalian cells could provide a better understanding of biological functions of native or modified proteins, and would allow the design of new gene constructs encoding peptides that mimic or block ligand interaction with target tissues. To identify the hGH domains responsible for induction of adipose differentiation we constructed hGH/hPL chimeric molecules using homologous DNA mutagenesis, since hGH, but not human placental lactogen (hPL), promotes adipose differentiation in mouse 3T3-F442A cells. We assayed their adipogenic activity in an autocrine/paracrine biological model consisting of transiently transfected 3T3-F442A cells with the chimeric constructs. Plasmid DNAs carrying these constructs were transfected into growing 3T3-F442A cells, and cultures were further maintained for 7 days to differentiate into adipocytes. Secretion of transfected hGH/hPL chimeric proteins into the medium was in the range of 5-25 ng/ml. Adipogenic activity was a property only of those chimeric proteins that contained hGH exon III together with either hGH exon II or hGH IV. Our results also suggest that hGH binding site-2 is composed of two structural subdomains: subsite 2A encoded by exon II of hGH and subsite-2B encoded by exon IV. We also suggest that full adipogenic activity requires the presence of binding site-1 and any of the subsites of binding site-2. This simple autocrine/paracrine biological model of gene transfection allows the analysis of specific biological activity of products encoded by modified genes.

Spatial and temporal targeting of gene expression in Drosophila by means of a tetracycline-dependent transactivator system.

In order to evaluate the efficiency of the tetracycline-regulated gene expression system in Drosophila, we have generated transgenic lines expressing a tetracycline-controlled transactivator protein (tTA), with specific expression patterns during embryonic and larval development. These lines were used to direct expression of a tTA-responsive promoter fused to the coding region of either the beta-galactosidase or the homeotic protein Antennapedia (ANTP), under various conditions of tetracycline treatment. We found that expression of beta-galactosidase can be efficiently inhibited in embryos and larvae with tetracycline provided in the food, and that a simple removal of the larvae from tetracycline exposure results in the induction of the enzyme in a time- and concentration-dependent manner. Similar treatments can be used to prevent the lethality associated with the ectopic expression of ANTP in embryos and, subsequently, to control the timing of expression of the homeoprotein ANTP specifically in the antennal imaginal disc. Our results show that the expression of a gene placed under the control of a tetracycline-responsive promoter can be tightly controlled, both spatially by the regulatory sequences driving the expression of tTA and temporally by tetracycline. This provides the basis of a versatile binary system for controlling gene expression in Drosophila, with an additional level of regulation as compared to the general method using the yeast transcription factor GAL4.

Nuclear magnetic resonance solution structure of the fushi tarazu homeodomain from Drosophila and comparison with the Antennapedia homeodomain.

The three-dimensional structure of a recombinant 70-residue polypeptide containing the complete fushi tarazu (ftz) homeodomain from Drosophila melanogaster has been determined by nuclear magnetic resonance (NMR) spectroscopy in solution. On the basis of 915 upper distance constraints derived from nuclear Overhauser effects and 178 dihedral angle constraints, a group of 20 conformers representing the solution structure of the ftz homeodomain was computed with the program DIANA and energy-minimized with the program OPAL. The average of the pairwise root-mean-square deviations of the individual NMR conformers relative to the mean coordinates is 0.50 A for the backbone atoms N, C alpha and C' of residues 8 to 53. The molecular architecture includes three helices comprising the residues 10 to 21, 28 to 38, and 42 to 52, a loop of residues 22 to 27 between the helices I and II, and a turn of residues 39 to 41 linking the helices II and III. Comparisons with the structure of the mutant Antennapedia homeodomain with Cys39 replaced by Ser, Antp (C39S), shows that the two proteins contain the same molecular fold for residues 8 to 53, whereas the more flexible fourth helix comprising residues 53 to 59 in the Antp (C39S) homeodomain has no counterpart in the ftz homeodomain. Considering that important intermolecular interactions in the DNA complexes with the Antp, engrailed and Mat alpha 2 homeodomains involve the fourth helix, it was rather unexpected that the stability of the complex of ftz with the BS2 operator site was found to be comparable to or even somewhat higher than that of the Antp complex with BS2. Another difference is that the Antp homeodomain is more stable with respect to thermal denaturation, with denaturation temperatures at pH 4.8 of 27 degrees C and 48 degrees C, respectively, for ftz and Antp.

The des(1-6)antennapedia homeodomain: comparison of the NMR solution structure and the DNA-binding affinity with the intact Antennapedia homeodomain.

The nuclear magnetic resonance (NMR) solution structure of an N-terminally truncated mutant Antennapedia homeodomain, des(1-6)Antp(C39S), has been determined from 935 nuclear Overhauser effect upper distance constraints and 148 dihedral angle constraints by using the programs DIANA and OPAL. Twenty conformers representing the solution structure of des(1-6)Antp(C39S) have an average root-mean-square distance relative to the mean coordinates of 0.56 A for the backbone atoms of residues 8-59. Comparison with the intact Antp(C39S) homeodomain shows that the two proteins have identical molecular architectures. The removal of the N-terminal residues 1-6, which are flexibly disordered in the intact homeodomain, causes only strictly localized structure variations and does not noticeably affect the adjoining helix I from residues 10-21. The DNA-binding constant of des(1-6)Antp(C39S) is approximately 10-fold reduced relative to the intact Antp(C39S) homeodomain, which can now be attributed to the absence of the previously reported contacts of the N-terminal polypeptide segment of the intact Antp(C39S) homeodomain with the minor groove of the DNA duplex.

HGH isoforms: cDNA expression, adipogenic activity and production in cell culture.

We have isolated, cloned and achieved functional expression of the cDNAs for both 22 kDa and 20 kDa human growth hormone (hGH) isoforms. A selective cDNA cloning strategy was used to preferentially and simultaneously obtain both hGH 22 kDa and hGH 20 kDa cDNAs. These were used to construct minigenes which were subcloned into two eukaryotic expression vectors and then introduced transiently in COS-7 cells and stably into CHO cells in culture. Transfection assays in COS-7 cells of both minigenes allowed the detection of the secreted hGH 22 kDa and hGH 20 kDa. These hGHs isoforms secreted into COS-7 medium were able to specifically promote differentiation of 3T3-F442A preadipocytes to adipose cells. Adipocyte differentiation was quantitated by Oil Red O triacylglycerol staining or glycerophosphate dehydrogenase activity. Furthermore, stable CHO cell lines have been derived that produce these hGH isoforms.

The human placental lactogen genes: structure, function, evolution and transcriptional regulation.

hPL is a member of an evolutionarily related gene family including hGH and hPRL. Expression of hPL is limited to the placenta but its physiological actions are far reaching. hPL has a direct somatotropic effect on fetal tissues, it alters maternal carbohydrate and lipid metabolism to provide for fetal nutrient requirements, and aids in stimulation of mammary cell proliferation. Two hPL genes (hPL3 and hPL4) encoding identical proteins are responsible for the production of up to 1-3 g PL hormone/day. Recent studies have characterized the regulatory controls of hPL expression. At the post transcriptional level, RNA stability may contribute to variable levels of hPL3 vs. hPL4 production. In addition, non-tissue-specific protein-promoter interactions involving the Sp1 transcription factor are necessary for hPL transcription initiation. A transcriptional enhancer located 3' to the hPL3 gene is responsible for the placenta-specific expression of this gene, while an additional enhancer may be located 3' to the hPl4 gene. The hPL enhancer is bound by multiple proteins including at least one placental specific protein that interacts with a TEF-1 motif. Therefore, enhancer-protein interactions most likely play a large part in the high levels of placenta-specific hPL expression.

Expression studies of transfected multigene families by homologous DNA mutagenesis.

A valuable approach for multigene family studies where the expression product of at least one gene member of the family is measurable is described. In such cases, the effect on gene expression of nucleotide sequence differences or mutations occurring in other members of the family or at alleles can easily be determined. This is achieved by a strategy called homologous DNA mutagenesis. It consists of the insertion of mutated regions from homologous genes into the context of the gene coding for the assayable product. Here we demonstrate the feasibility of this approach using gene members of the human growth hormone and human placental lactogen (hGH-hPL) multigene family.

Coding potential of transfected human placental lactogen genes.

We have joined the promoter-less sequences of the three hPL genes (hPL-1, hPL-3 and hPL-4) to strong transcriptional control elements. in vivo 35S-labeled proteins from the culture medium of cells transfected with the genes were resolved on SDS-polyacrylamide gels. The presence of characteristic labeled bands, visualized by autoradiography, determined that hPL-4 and hPL-3, but not hPL-1, contribute to the production of mature hPL. In these experiments hPL-3 expressed more RNA and protein than hPL-4. By exchanging the first two exons among hPL and hGH genes, we determined that the abundance of chimeric proteins depended on the genetic origin of the first two exons. Finally, we found evidence indicating that the splice mutation (G----A) at the beginning of the second intron of hPL-1, is not the only cause of the apparent lack of inactivity of this gene, since its reversion does not restore expression.

New vectors for the efficient expression of mammalian genes in cultured cells.

We have constructed a new pair of plasmid vectors for the efficient expression of mammalian genes. The first of the new plasmids, pAVE1, was derived from pCMVcat [Foecking and Hofstetter, Gene 45 (1986) 101-105] by replacing the chloramphenicol acetyltransferase-encoding sequences in the latter for a multiple cloning site. Since it possesses the powerful enhancer-promoter unit of the immediate early gene of human cytomegalovirus, pAVE1 is ideal for the expression of mammalian genes. The second expression vector, pAVE2, resulted when the 3'-end flanking region from the human growth hormone-encoding gene (hGH) was incorporated in pAVE1. This region provides sequences for 3'-end processing and polyadenylation of primary transcripts. Thus, pAVE2 is suitable for expression of cDNAs in cultured cells, where introns have little effect on gene expression. To test our new vectors, we inserted the structural region of the chromosomal hGH gene into pAVE1, and its cDNA into pAVE2. By independently transfecting the resulting recombinant plasmids into COS-7 cells, we have achieved high levels of hGH transient expression with both vectors.

Low-speed purification of human placental nuclei.

A simple method for the purification of human placental nuclei is described. Nuclei were isolated by homogenizing tissue in standard saline citrate solution in the presence of zinc chloride to stabilize the nuclear membranes, NP40 as non-ionic detergent and sodium bisulphite for inhibition of proteolytic activity. Nuclei purification was achieved by low-speed centrifugation through a discontinuous sucrose gradient. The purified nuclei were evaluated by morphological criteria using phase contrast and electron microscopy. The extent of contamination by cytoplasmic debris was estimated by Papanicolaou's staining technique. Biochemical criteria include measurements of alkaline phosphatase activity as a plasma membrane enzyme marker and DNA-dependent RNA polymerase activity for the functional integrity of nuclear components. Transcriptionally active nuclei were obtained but the yield of nuclei was low; however, this low yield is compensated by the high degree of purity, the simplicity of the method and the functional and morphological integrity of the purified nuclei.