When pol I goes into high gear: processive DNA synthesis by pol I in the cell

Pol I is the most abundant polymerase in E. coli and plays an important role in short patch repair. In accord with this role in the cell, the purified polymerase exhibits low processivity and high fidelity in vitro. Pol I is also the polymerase responsible for leader strand synthesis during ColE1 plasmid replication. In a previous publication, we described the generation of a highly error-prone DNA polymerase I. Expression of this mutant Pol I results in errors during the replication of a ColE1 plasmid. The distribution and spectrum of mutations in the ColE1 plasmid sequence downstream the ori indicates that Pol I is capable of more processive replication in vivo than previously accepted. Here, we review evidence suggesting that Pol I may be recruited into a replisome-like holoenzyme and speculate that processive DNA replication by Pol I may play a role in recombination-dependent DNA replication in the cell.     

Epigenetic activation of SOX11 in lymphoid neoplasms by histone modifications

Recent studies have shown aberrant expression of SOX11 in various types of aggressive B-cell neoplasms. To elucidate the molecular mechanisms leading to such deregulation, we performed a comprehensive SOX11 gene expression and epigenetic study in stem cells, normal hematopoietic cells and different lymphoid neoplasms. We observed that SOX11 expression is associated with unmethylated DNA and presence of activating histone marks (H3K9/14Ac and H3K4me3) in embryonic stem cells and some aggressive B-cell neoplasms. In contrast, adult stem cells, normal hematopoietic cells and other lymphoid neoplasms do not express SOX11. Such repression was associated with silencing histone marks H3K9me2 and H3K27me3. The SOX11 promoter of non-malignant cells was consistently unmethylated whereas lymphoid neoplasms with silenced SOX11 tended to acquire DNA hypermethylation. SOX11 silencing in cell lines was reversed by the histone deacetylase inhibitor SAHA but not by the DNA methyltransferase inhibitor AZA. These data indicate that, although DNA hypermethylation of SOX11 is frequent in lymphoid neoplasms, it seems to be functionally inert, as SOX11 is already silenced in the hematopoietic system. In contrast, the pathogenic role of SOX11 is associated with its de novo expression in some aggressive lymphoid malignancies, which is mediated by a shift from inactivating to activating histone modifications.     

Chromatin organization during spermiogenesis in Octopus vulgaris. II: DNA-interacting proteins

In this article we study the proteins responsible for chromatin condensation during spermiogenesis in the cephalopod Octopus vulgaris. The DNA of ripe sperm nuclei in this species is condensed by a set of five different proteins. Four of these proteins are protamines. The main protamine (Po2), a protein of 44 amino acid residues, is extraordinarily simple (composed of only three different amino acid types: arginine (R), serine (S), and glycine (G). It is a basic molecule consisting of 79.5 mol% arginine residues. The rest of the protamines (Po3, Po4, Po5) are smaller molecules (33, 28, and 30 amino acid residues, respectively) that are homologous among themselves and probably with the main Po2 protamine. The ripe sperm nucleus of O. vulgaris also contains a small quantity of a molecule (Po1) that is similar to Po2 protamine. This protein could represent a Po2 protamine-precursor in a very advanced step of its processing. We discuss the characteristics of these proteins, as well as the relation between the complexity of chromatin condensation and the transitions of nuclear proteins during spermiogenesis in O. vulgaris.     

JNK signaling pathway required for wound healing in regenerating Drosophila wing imaginal discs

We have examined wound healing during regeneration of Drosophila wing imaginal discs fragments by confocal microscopy and assessed the role of components of the JNK pathway in this process. After cutting, columnar and peripodial epithelia cells at the wound edge start to close the wound through formation and contraction of an actin cable. This is followed by a zipping process through filopodial protrusions from both epithelia knitting the wound edges from proximal to distal areas of the disc. Activation of the JNK pathway is involved in such process. puckered (puc) expression is induced in several rows of cells at the edge of the wound, whereas absence of JNK pathway activity brought about by hemipterous, basket, and Dfos mutants impair wound healing. These defects are accompanied by lowered or loss of expression of puc. In support of a role of puc in wound healing, hep mutant phenotypes are rescued by reducing puc function, whereas overexpression of puc inhibits wound healing. Altogether, these results demonstrate a role for the JNK pathway in imaginal disc wound healing, similar to that reported for other healing processes such as embryonic dorsal closure, thoracic closure, and adult epithelial wound healing in Drosophila. Differences with such processes are also highlighted.     

Fast activated charcoal prepurification of Fusarium solani β-glucosidase for an efficient oleuropein bioconversion

Fungal β-glucosidases were extensively studied regarding their various potential biotechnology applications. Here, we report the selection of Fusarium solani strain producing high yield of β-glucosidase activity. The effect of some factors on β-glucosidase production was studied including: Initial pH, medium composition, concentration of carbon and nitrogen sources, and particle size of raw substrates. The optimal enzyme production was obtained with 4?units of pH. The highest β-glucosidase activity was produced on 4% wheat bran (WB) as raw carbon sources, reaching 5?U/mL. A positive correlation between WB particle size and the β-glucosidase production level was settled. The last one was enhanced to 13.60?U/mL in the presence of 0.5% (w/v) of ammonium sulfate. Interestingly, the activated charcoal was used as an inexpensive reagent enabling a rapid and efficient purification prior step that improved the enzyme-specific activity. Eventually, F. solani β-glucosidase acts efficiently during the bioconversion process of oleuropein. Indeed, 82.5% of oleuropein was deglycosylated after 1?hr at 40°C. Altogether, our data showed that the β-glucosidase of F. solani has a potential application to convert oleuropein to ameliorate food quality.     

Integrating ultrasonography within the reproductive management of the collared peccary (Tayassu tajacu)

Ultrasound imaging has been used to elucidate certain aspects of the reproductive biology of wild or endangered species. However, to our knowledge, this tool has not been used for reproductive monitoring of the collared peccary (Tayassu tajacu). In this study, real-time ultrasonography was used in 16 collared peccary females to diagnose early pregnancy status and predict gestational age. Based on the detection of an embryo, the earliest pregnancy diagnosis was made on Day 18 after mating, with the mean time needed for diagnosis being 22 days. Overall accuracies on Days 22, 26 and 28 were 56, 93, and 100%, respectively. On Days 26 and 28, all pregnancy and non-pregnancy diagnoses, respectively, were correct. The fetal measurements that best correlated with gestational age were crown-rump-length (CRL) and the length and diameter of the thorax. CRL was considered the most practical measurement because, contrary to thoracic fetometry, it could be determined when the embryo was first detected. Our findings revealed real-time ultrasound scanning to be a very accurate method for early pregnancy diagnosis and prediction of gestational age in the collared peccary.     

Notch signaling is essential for ventricular chamber development

Ventricular chamber morphogenesis, first manifested by trabeculae formation, is crucial for cardiac function and embryonic viability and depends on cellular interactions between the endocardium and myocardium. We show that ventricular Notch1 activity is highest at presumptive trabecular endocardium. RBPJk and Notch1 mutants show impaired trabeculation and marker expression, attenuated EphrinB2, NRG1, and BMP10 expression and signaling, and decreased myocardial proliferation. Functional and molecular analyses show that Notch inhibition prevents EphrinB2 expression, and that EphrinB2 is a direct Notch target acting upstream of NRG1 in the ventricles. However, BMP10 levels are found to be independent of both EphrinB2 and NRG1 during trabeculation. Accordingly, exogenous BMP10 rescues the myocardial proliferative defect of in vitro-cultured RBPJk mutants, while exogenous NRG1 rescues differentiation in parallel. We suggest that during trabeculation Notch independently regulates cardiomyocyte proliferation and differentiation, two exquisitely balanced processes whose perturbation may result in congenital heart disease.