Isolation and characterization of marsupial IL5 genes

The genomic nucleotide sequence and chromosomal position of the interleukin 5 (IL5) gene has been described for the model marsupial Macropus eugenii (tammar wallaby). A 272 base pair genomic IL5 polymerase chain reaction (PCR) product spanning exon 3, intron 3, and exon 4 was generated using stripe-faced dunnart (Sminthopsis macroura) DNA. This PCR product was used to isolate a genomic lambda clone containing the complete IL5 gene from a tammar wallaby EMBL3 lambda library. Sequencing revealed that the tammar wallaby IL5 gene consists of four exons separated by three introns. Comparison of the marsupial coding sequence with coding sequences from eutherian species revealed 61 to 69% identity at the nucleotide level and 48 to 63% identity at the amino acid (aa) level. A polymorphic complex compound microsatellite was identified within intron 2 of the tammar wallaby IL5 gene. This microsatellite was also found in other marsupials including the swamp wallaby, tree kangaroo, stripe-faced dunnart, South American opossum, brushtail possum, and koala. Fluorescence in situ hybridization using DNA from the IL5 clone on tammar wallaby chromosomes indicated that the IL5 gene is located on Chromosome 1.     

Genetic diversity of Couratari multiflora and Couratari guianensis (Lecythidaceae): consequences of two types of rarity in central Amazonia

We quantified the within-population genetic variation of Couratari multiflora and C. guianensis, two tree species found in terra firme forests of central Amazonia. Both species have some ecological features in common, but they differ in population abundance across their geographic ranges. While C. multiflora has been found only in low-density populations in all sites studied to date, C. guianensis is relatively common in some sites and very scarce in others. In a 400-ha plot, we found 41 and 29 adults of C. multiflora and C. guianensis, respectively. Twenty-two saplings of C. guianensis and 103 seedlings of C. multiflora were also examined. The mean expected heterozygosities (H_em) of seedlings and adults of C. multiflora were 0.431 and 0.436, and the mean fixation indices (F_m), 0.114 and 0.176, respectively. For C. guianensis, saplings and adults presented H_em equal to 0.425 and 0.429, and the F_m were 0.393 and 0.527, respectively. These low-density populations of two congeneric species did not differ in terms of genetic diversity, but rather they differed in terms of mean observed heterozygosity (H_om), and therefore F_m. The species with variable population density had lower H_om and greater F_m relative to the species that is always found in low-density.     

Immunohistochemical Analysis of DNA ‘mismatch-repair’ Enzyme Human Mut-S-Homologon-2 in Ovarian Carcinomas

The human Mut-S-Homologon-2 (hMSH-2) gene product is a member of a highly conserved family of proteins involved in postreplication mismatch repair. We have analysed hMSH-2 expression in normal ovarian tissue (n=15) and ovarian carcinomas (n=40). hMSH-2 protein was investigated immunohistochemically on frozen sections using a highly sensitive streptavidin–peroxidase technique and a specific mouse monoclonal antibody (clone FE11). A hMSH-2-immunoreactivity score (hMSH-2-IRS) for semiquantitative analysis of hMSH-2 expression is presented. In normal ovarian tissue, we only found weak nuclear immunoreactivity for hMSH-2 in 60%, while the remaining 40% were hMSH-2 negative (mean hMSH-2-IRS: 0.73; SD: ±0.70). All ovarian carcinomas analysed revealed moderate to strong nuclear immunoreactivity (mean hMSH-2-IRS: 8.05; SD: ±3.65). hMSH-2 staining was heterogeneous, with visual differences between individual tumour cells. Expression of hMSH-2 protein was consistently and strongly upregulated in tumour cells of ovarian carcinomas as compared to normal ovarian tissue. No statistically significant correlation in comparing the labelling patterns for hMSH-2 with the labelling patterns for Ki-67 (mean percentage of Ki-67 positive tumour cells: 25.88%; SD: ±18.43) was observed in ovarian carcinomas. Furthermore, no statistical significant correlations between hMSH-2-IRS and histological grading (p=0.47), histological type of carcinoma (p=0.706) or FIGO-classification (p=0.054) were found. Our findings indicate that (a) hMSH-2 is expressed in normal human ovarian tissue, (b) expression of hMSH-2 is increased in ovarian carcinomas, (c) expression of hMSH-2 may be of importance for the genetic stability of ovarian carcinomas in vivo, (d) hMSH-2 mutations may not cause microsatellite instability in ovarian carcinomas, (e) hMSH-2 may contribute to mechanisms responsible for resistance to anticancer drugs.     

Direct involvement of p53 in the base excision repair pathway of the DNA repair machinery

The p53 tumor suppressor that plays a central role in the cellular response to genotoxic stress was suggested to be associated with the DNA repair machinery which mostly involves nucleotide excision repair (NER). In the present study we show for the first time that p53 is also directly involved in base excision repair (BER). These experiments were performed with p53 temperature-sensitive (ts) mutants that were previously studied in in vivo experimental models. We report here that p53 ts mutants can also acquire wild-type activity under in vitro conditions. Using ts mutants of murine and human origin, it was observed that cell extracts overexpressing p53 exhibited an augmented BER activity measured in an in vitro assay. Depletion of p53 from the nuclear extracts abolished this enhanced activity. Together, this suggests that p53 is involved in more than one DNA repair pathway.     

Biochemical Characterization of Fungal Phytases (myo-Inositol Hexakisphosphate Phosphohydrolases): Catalytic Properties

Supplementation with phytase is an effective way to increase the availability of phosphorus in seed-based animal feed. The biochemical characteristics of an ideal phytase for this application are still largely unknown. To extend the biochemical characterization of wild-type phytases, the catalytic properties of a series of fungal phytases, as well as Escherichia coli phytase, were determined. The specific activities of the fungal phytases at 37°C ranged from 23 to 196 U · (mg of protein)⁻¹, and the pH optima ranged from 2.5 to 7.0. When excess phytase was used, all of the phytases were able to release five phosphate groups of phytic acid (myo-inositol hexakisphosphate), which left myo-inositol 2-monophosphate as the end product. A combination consisting of a phytase and Aspergillus niger pH 2.5 acid phosphatase was able to liberate all six phosphate groups. When substrate specificity was examined, the A. niger, Aspergillus terreus, and E. coli phytases were rather specific for phytic acid. On the other hand, the Aspergillus fumigatus, Emericella nidulans, and Myceliophthora thermophila phytases exhibited considerable activity with a broad range of phosphate compounds, including phenyl phosphate, p-nitrophenyl phosphate, sugar phosphates, α- and β-glycerophosphates, phosphoenolpyruvate, 3-phosphoglycerate, ADP, and ATP. Both phosphate liberation kinetics and a time course experiment in which high-performance liquid chromatography separation of the degradation intermediates was used showed that all of the myo-inositol phosphates from the hexakisphosphate to the bisphosphate were efficiently cleaved by A. fumigatus phytase. In contrast, phosphate liberation by A. niger or A. terreus phytase decreased with incubation time, and the myo-inositol tris- and bisphosphates accumulated, suggesting that these compounds are worse substrates than phytic acid is. To test whether broad substrate specificity may be advantageous for feed application, phosphate liberation kinetics were studied in vitro by using feed suspensions supplemented with 250 or 500 U of either A. fumigatus phytase or A. niger phytase (Natuphos) per kg of feed. Initially, phosphate liberation was linear and identical for the two phytases, but considerably more phosphate was liberated by the A. fumigatus phytase than by the A. niger phytase at later stages of incubation.     

Multi-domain, cell-envelope proteinases of lactic acid bacteria

The multi-domain, cell-envelope proteinases encoded by the genes prtB of Lactobacillus delbrueckii subsp. bulgaricus, prtH of Lactobacillus helveticus, prtP of Lactococcus lactis, scpA of Streptococcus pyogenes and csp of Streptococcus agalactiae have been compared using multiple sequence alignment, secondary structure prediction and database homology searching methods. This comparative analysis has led to the prediction of a number of different domains in these cell-envelope proteinases, and their homology, characteristics and putative function are described. These domains include, starting from the N-terminus, a pre-pro-domain for secretion and activation, a serine protease domain (with a smaller inserted domain), two large middle domains A and B of unknown but possibly regulatory function, a helical spacer domain, a hydrophilic cell-wall spacer or attachment domain, and a cell-wall anchor domain. Not all domains are present in each cell-envelope proteinase, suggesting that these multi-domain proteins are the result of gene shuffling and domain swapping during evolution.     

Thermoregulated Expression and Characterization of an NAD(P)H-Dependent 2-Cyclohexen-1-one Reductase in the Plant Pathogenic Bacterium Pseudomonas syringae pv. glycinea

The phytopathogenic bacterium Pseudomonas syringae pv. glycinea PG4180.N9 causes bacterial blight of soybeans and preferably infects its host plant during periods of cold, humid weather conditions. To identify proteins differentially expressed at low temperatures, total cellular protein fractions derived from PG4180.N9 grown at 18 and 28°C were separated by two-dimensional gel electrophoresis. Of several proteins which appeared to be preferentially present at 18°C, a 40-kDa protein with an isoelectric point of approximately 5 revealed significant N-terminal sequence homology to morphinone reductase (MR) of Pseudomonas putida M10. The respective P. syringae gene was isolated from a genomic cosmid library of PG4180, and its nucleotide sequence was determined. It was designated ncr for NAD(P)H-dependent 2-cyclohexen-1-one reductase. Comparison of the 1,083-bp open reading frame with database entries revealed 48% identity and 52% similarity to the MR-encoding morB gene of P. putida M10. The ncr gene was overexpressed in Escherichia coli, and its gene product was used to generate polyclonal antisera. Purified recombinant Ncr protein was enzymatically characterized with NAD(P)H and various morphinone analogs as substrates. So far, only 2-cyclohexen-1-one and 3-penten-2-one were found to be substrates for Ncr. By high-pressure liquid chromatography analysis, flavin mononucleotide could be identified as the noncovalently bound prosthetic group of this enzyme. The distribution of the ncr gene in different Pseudomonas species and various strains of P. syringae was analyzed by PCR and Southern blot hybridization. The results indicated that the ncr gene is widespread among P. syringae pv. glycinea strains but not in other pathovars of P. syringae or in any of the other Pseudomonas strains tested.     

Optimized expression and purification of adipose triglyceride lipase improved hydrolytic and transacylation activities in vitro

Adipose triglyceride lipase (ATGL) plays a key role in intracellular lipolysis, the mobilization of stored triacylglycerol. This work provides an important basis for generating reproducible and detailed data on the hydrolytic and transacylation activities of ATGL. We generated full-length and C-terminally truncated ATGL variants fused with various affinity tags and analyzed their expression in different hosts, namely E.coli, the insect cell line Sf9, and the mammalian cell line human embryonic kidney 293T. Based on this screen, we expressed a fusion protein of ATGL covering residues M1-D288 flanked with N-terminal and C-terminal purification tags. Using these fusions, we identified key steps in expression and purification protocols, including production in the E. coli strain ArcticExpress (DE3) and removal of copurified chaperones. The resulting purified ATGL variant demonstrated improved lipolytic activity compared with previously published data, and it could be stimulated by the coactivator protein comparative gene identification-58 and inhibited by the protein G0/G1 switch protein 2. Shock freezing and storage did not affect the basal activity but reduced coactivation of ATGL by comparative gene identification 58. In vitro, the truncated ATGL variant demonstrated acyl-CoA–independent transacylation activity when diacylglycerol was offered as substrate, resulting in the formation of fatty acid as well as triacylglycerol and monoacylglycerol. However, the ATGL variant showed neither hydrolytic activity nor transacylation activity upon offering of monoacylglycerol as substrate. To understand the role of ATGL in different physiological contexts, it is critical for future studies to identify all its different functions and to determine under what conditions these activities occur.