RECQ1 helicase interacts with human mismatch repair factors that regulate genetic recombination

Understanding the molecular and cellular functions of RecQ helicases has attracted considerable interest since several human diseases characterized by premature aging and/or cancer have been genetically linked to mutations in genes of the RecQ family. Although a human disease has not yet been genetically linked to a mutation in RECQ1, the prominent roles of RecQ helicases in the maintenance of genome stability suggest that RECQ1 helicase is likely to be important in vivo.To acquire a better understanding of RECQ1 cellular and molecular functions, we have investigated its protein interactions. Using a co-immunoprecipitation approach, we have identified several DNA repair factors that are associated with RECQ1 in vivo. Direct physical interaction of these repair factors with RECQ1 was confirmed with purified recombinant proteins. Importantly, RECQ1 stimulates the incision activity of human exonuclease 1 and the mismatch repair recognition complex MSH2/6 stimulates RECQ1 helicase activity. These protein interactions suggest a role of RECQ1 in a pathway involving mismatch repair factors. Regulation of genetic recombination, a proposed role for RecQ helicases, is supported by the identified RECQ1 protein interactions and is discussed.     

Curcumin regulates expression and activity of matrix metalloproteinases 9 and 2 during prevention and healing of indomethacin-induced gastric ulcer

Matrix metalloproteinases (MMPs) are suggested to play a critical role in extracellular matrix degradation and remodeling during inflammation and wound healing processes. However, the role of MMPs in indomethacin-induced gastric ulcer and its healing process are not clearly understood. This study is aimed at determining the regulation of MMP-9 and -2 activities in indomethacin-induced acute gastric ulceration and healing. Indomethacin-ulcerated stomach extracts exhibit significant up-regulation of pro-MMP-9 (92 kDa) activity and moderate reduction of MMP-2 activity, which strongly correlate with indomethacin dose and severity of ulcer. The anti-inflammatory and antioxidant properties of curcumin, an active component of turmeric, suggest that curcumin may exert antiulcer activity through scavenging reactive oxygen species, by regulating MMP activity, or both. To test these possibilities, the effect of curcumin in indomethacin-induced gastric ulcer is examined by biochemical and histological methods. The results show that curcumin exhibits potent antiulcer activity in acute ulcer in rat model by preventing glutathione depletion, lipid peroxidation, and protein oxidation. Denudation of epithelial cells during damage of gastric lumen is reversed by curcumin through re-epithelialization. Furthermore, both oral and intraperitoneal administration of curcumin blocks gastric ulceration in a dose-dependent manner. It accelerates the healing process and protects gastric ulcer through attenuation of MMP-9 activity and amelioration of MMP-2 activity. Omeprazole, an established antiulcer drug does not inhibit MMP-9 while protecting indomethacin-induced gastric ulcer. We conclude that antiulcer activity of curcumin is primarily attributed to MMP-9 inhibition, one of the major path-ways of ulcer healing.     

Novel quantitative tools for engineering analysis of hepatocyte cultures in bioartificial liver systems

Extracorporeal bioartificial liver devices (BAL) are perhaps among the most promising technologies for the treatment of liver failure, but significant technical challenges remain in order to develop systems with sufficient processing capacity and of manageable size. One key limitation is that during BAL operation, when the device is exposed to plasma from the patient, hepatocytes are prone to accumulate intracellular lipids and exhibit poor liver-specific functions. Based on hepatic intermediary metabolism, we have utilized mathematical programming techniques to optimize the biochemical environment of hepatocyte cultures towards the desired effect of increased albumin and urea synthesis. To investigate the feasible range of optimal hepatic function, we have obtained a Pareto optimal set of solutions corresponding to liver-specific functions of urea and albumin secretion in the metabolic framework using multiobjective optimization. The importance of amino acids in the supplementation and the criticality of the metabolic pathways have been investigated using logic-based programming techniques. Since the metabolite measurements are bound to be patient specific, and hence subject to variability, uncertainty has to be integrated with system analysis to improve the prediction of hepatic function. We have used the concept of two stage stochastic programming to obtain robust solutions by considering extracellular variability. The proposed analysis represents a new systematic approach to analyze behavior of hepatocyte cultures and optimize different operating parameters for an extracorporeal device based on real-time conditions.     

Ultrastructural identification of uncoated caveolin-independent early endocytic vehicles

Using quantitative light microscopy and a modified immunoelectron microscopic technique, we have characterized the entry pathway of the cholera toxin binding subunit (CTB) in primary embryonic fibroblasts. CTB trafficking to the Golgi complex was identical in caveolin-1null (Cav1-/-) mouse embryonic fibroblasts (MEFs) and wild-type (WT) MEFs. CTB entry in the Cav1-/- MEFs was predominantly clathrin and dynamin independent but relatively cholesterol dependent. Immunoelectron microscopy was used to quantify budded and surface-connected caveolae and to identify noncaveolar endocytic vehicles. In WT MEFs, a small fraction of the total Cav1-positive structures were shown to bud from the plasma membrane (2% per minute), and budding increased upon okadaic acid or lactosyl ceramide treatment. However, the major carriers involved in initial entry of CTB were identified as uncoated tubular or ring-shaped structures. These carriers contained GPI-anchored proteins and fluid phase markers and represented the major vehicles mediating CTB uptake in both WT and caveolae-null cells.     

Mature embryo axis-based high frequency somatic embryogenesis and plant regeneration from multiple cultivars of barley (Hordeum vulgare L.)

A highly reproducible regeneration system through somatic embryogenesis from the excised mature embryos (MEs) of dry seeds of a range of European barley cultivars was developed. By minimizing the germination of plated MEs, primary callus could be obtained with high frequency which permitted efficient embryogenesis and regeneration of a large number of green plants. Different approaches were tested to reduce or prevent normal germination: (i) the use of a well defined balance of maltose and 2,4-D in the induction medium, (ii) soaking of seeds in water containing 2,4-D solution, (iii) direct culture of excised embryonic axes, (iv) longitudinally bisected MEs giving two halves, and (v) complete removal of the elongated main shoot including any roots within a week of culture initiation. Culturing of bisected MEs and whole embryonic axes gave the best responses with respect to large amounts of callus combined with minimal germination. The incorporation of BAP at low levels in the medium was found to be most effective for embryogenesis and the maintenance of long-term morphogenic capacity (more than 11 months up to now). This procedure allows the complete regeneration of plants in 16-20 weeks, from the initial isolation of MEs through all the steps to the development of plants ready to be transferred to the soil. The protocol was first developed for cv. Golden Promise and successfully applied to commercial cultivars. All cultivars tested formed embryogenic callus, with overall rates ranging from 22-55% and an average number of green plants per embryogenic callus from 1.5 to 7.5 across the genotypes.     

Actin microridges characterized by laser scanning confocal and atomic force microscopy

We have characterized the cell surface of zebrafish stratified epithelium using a combined approach of light and atomic force microscopy under conditions which simulate wound healing. Microridges rise on average 100 nm above the surface of living epithelial cells, which correlate to bundles of cytochalasin B-insensitive actin filaments. Time-lapse microscopy revealed the bundles to form a highly dynamic network on the cell surface, in which bundles and junctions were severed and annealed on a time scale of minutes. Atomic force microscopy topographs further indicated that actin bundle junctions identified were of two types: overlaps and integrated end to side T- and Y-junctions. The surface bundle network is found only on the topmost cell layer of the explant, and never on individual locomoting cells. Possible functions of these actin bundles include cell compartmentalization of the cell surface, resistance to mechanical stress, and F-actin storage.     

Bovine adenovirus type 3 internalization is independent of primary receptors of human adenovirus type 5 and porcine adenovirus type 3

Usefulness of adenoviral vectors derived from human adenovirus (HAd) type 5 (HAd5) is mainly limited by wide prevalence of preexisting anti-HAd5 immunity as well as non-specific tissue tropism of these vectors. As an alternative, non-human adenoviral vectors including bovine adenovirus type 3 (BAd3) are currently being investigated. Non-prevalence of BAd3 in humans and its ability to evade preexisting HAd immunity are some of the features that make BAd3 a promising vector for human gene delivery. BAd3 appears to have a tissue tropism distinct from that of HAd5 and also the repertoire of cells efficiently transduced by BAd3 is different. We performed antibody-mediated receptor blocking experiments to show that BAd3 internalization was independent of coxsackievirus-adenovirus receptor, the primary determinant of HAd5 tropism, or integrin alpha(v)beta3, a secondary molecule involved in HAd5 entry. Using homologous and heterologous knob-mediated competition assays with recombinant knobs of HAd5, porcine adenovirus type 3 (PAd3), or BAd3, we observed that BAd3 internalization was independent of the primary receptors of HAd5 and PAd3. These results provide support for further exploration of BAd3 vectors for designing targeted vectors for human gene therapy.