(+)-CC-1065 as a structural probe of Mu transposase-induced bending of DNA: overcoming limitations of hydroxyl-radical footprinting

Phage Mu transposase (A-protein) is primarily responsible for transposition of the Mu genome. The protein binds to six att sites, three at each end of Mu DNA. At most att sites interaction of a protein monomer with DNA is seen to occur over three minor and two consecutive major grooves and to result in bending up to about 90 degrees. To probe the directionality and locus of these A-protein-induced bends, we have used the antitumor antibiotic (+)-CC-1065 as a structural probe. As a consequence of binding within the minor groove, (+)-CC-1065 is able to alkylate N3 of adenine in a sequence selective manner. This selectivity is partially determined by conformational flexibility of the DNA sequence, and the covalent adduct has a bent DNA structure in which narrowing of the minor groove has occurred. Using this drug in experiments in which either gel retardation or DNA strand breakage are used to monitor the stability of the A-protein--DNA complex or the (+)-CC-1065 alkylation sites on DNA (att site L3), we have demonstrated that of the three minor grooves implicated in the interaction with A-protein, the peripheral two are 'open' or accessible to drug bonding following protein binding. These drug-bonding sites very likely represent binding at at least two A-protein-induced bending sites. Significantly, the locus of bending at these sites is spaced approximately two helical turns apart, and the bending is proposed to occur by narrowing of the minor groove of DNA. The intervening minor groove between these two peripheral sites is protected from (+)-CC-1065 alkylation. The results are discussed in reference to a proposed model for overall DNA bending in the A-protein att L3 site complex. This study illustrates the utility of (+)-CC-1065 as a probe for protein-induced bending of DNA, as well as for interactions of minor groove DNA bending proteins with DNA which may be masked in hydroxyl radical footprinting experiments.     

Immunoreactivity of Brazilian HIV isolates with different V3 motifs

The influence of noncompetitive (MK-801), competitive (AP-7) and the antagonist of polyamines site of NMDA receptor (arcaine) on the central activity of angiotensin II (A II) was studied. The open field test, conditioning of active avoidance responses (CARs) and passive avoidance situation was used to investigate learning and memory in rats. All used antagonists decreased beneficial action of A II on these processes.     

Evaluation of the aortic root by MRI: insights from patients with homozygous familial hypercholesterolemia

Hepatitis C chronically infects approximately 1.5% of Americans and is the most common clinical problem facing hepatologists. Since the virus was initially described in 1989, development of an effective therapy has been challenging. Although several different therapeutic agents have been used, no therapy has been shown to reliably eradicate the virus. Interferon-alpha, a cytokine with immunostimulatory and anti-viral properties, has become the therapy of choice for patients with chronic hepatitis C infection. Trials assessing the efficacy of interferon-alpha have characterized host and viral factors predictive of responses to treatment. A thorough understanding of these predictive factors is requisite to providing cost-effective therapeutic decisions for the patient with chronic hepatitis C infection.     

Mechanical effects of different localization of the point of entry in femoral nailing

Treatments of Chinese hamster V79 cells during one cell cycle with a new type of topoisomerase II inhibitor, ICRF-193, which does not accumulate cleavable topoisomerase-DNA complexes induced both chromosome- and chromatid-type aberrations with high frequencies. Furthermore, ICRF-193 synergistically enhanced the yield of UVB-induced chromatid-type aberrations, chromatid exchanges in particular. Treated with ICRF-193 for the last 3 h before harvest, cells showed frequent incidence of chromatid-type aberrations and synergistic enhancement of UVB-induced chromatid-type aberrations, chromatid exchanges in particular. These results suggest that spontaneous and UVB-induced lesions might be ultimately transformed into chromatid-type aberrations by topoisomerase II-dependent checkpoint process(es) in the G2 phase of the cell cycle.     

Psychological aspects of systemic lupus erythematosus: cognitive function, mood, and self-report

Previous studies have shown that Tetrahymena citrate synthase and the Tetrahymena 14-nm filament protein are encoded by a single gene and translated from one species of mRNA, and that they are identical in terms of molecular weight, antigenicity, and some enzymatic properties. In this study, using two-dimensional gel electrophoresis, we demonstrated that the citrate synthase comprised pI 7.7 and 8.0 isoforms, while the 14-nm filament protein comprised three isoforms with isoelectric points of 7.7, 8.0, and 8.4. The amino acid sequences of the NH2-terminal portions of all isoforms were identical and the peptide maps with V8 protease were almost the same. In addition, when the citrate synthase activity of each isoform was measured after separation by non-urea isoelectric focusing without denaturing treatment, the pI 7.7 and/or pI 8.0 isoforms exhibited the citrate synthase activity, but the pI 8.4 isoform only found for the 14-nm filament protein did not possess this activity. These results suggest that the polymorphism of these isoforms is caused by some posttranslational modifications, and that it may have resulted in the different compartmentalization and functions of Tetrahymena citrate synthase and the 14-nm filament protein.     

Metabolic impact of adenovirus-mediated overexpression of the glucose-6-phosphatase catalytic subunit in hepatocytes

Glucose-6-phosphatase (G6Pase) catalyzes the hydrolysis of glucose 6-phosphate (Glu-6-P) to free glucose and, as the last step in gluconeogenesis and glycogenolysis in liver, is thought to play an important role in glucose homeostasis. G6Pase activity appears to be conferred by a set of proteins localized to the endoplasmic reticulum, including a glucose-6-phosphate translocase, a G6Pase phosphohydrolase or catalytic subunit, and glucose and inorganic phosphate transporters in the endoplasmic reticulum membrane. In the current study, we used a recombinant adenovirus containing the cDNA encoding the G6Pase catalytic subunit (AdCMV-G6Pase) to evaluate the metabolic impact of overexpression of the enzyme in primary hepatocytes. We found that AdCMV-G6Pase-treated liver cells contain significantly less glycogen and Glu-6-P, but unchanged UDP-glucose levels, relative to control cells. Further, the glycogen synthase activity state was closely correlated with Glu-6-P levels over a wide range of glucose concentrations in both G6Pase-overexpressing and control cells. The reduction in glycogen synthesis in AdCMV-G6Pase-treated hepatocytes is therefore not a function of decreased substrate availability but rather occurs because of the regulatory effects of Glu-6-P on glycogen synthase activity. We also found that AdCMV-G6Pase-treated-cells had significantly lower rates of lactate production and [3-3H]glucose usage, coupled with enhanced rates of gluconeogenesis and Glu-6-P hydrolysis. We conclude that overexpression of the G6Pase catalytic subunit alone is sufficient to activate flux through the G6Pase system in liver cells. Further, hepatocytes treated with AdCMV-G6Pase exhibit a metabolic profile resembling that of liver cells from patients or animals with non-insulin-dependent diabetes mellitus, suggesting that dysregulation of the catalytic subunit of G6Pase could contribute to the etiology of the disease.     

Optic chiasm astrocytomas of childhood. 1. Long-term follow-up

There are many in vivo animal models for studying airway mucus secretion and hypersecretion, each with advantages and disadvantages. Use of a particular test system will depend upon the aspect of secretion to be modelled. Airway hypersecretory diseases exhibit chronic mucus hypersecretion, of which the clinical impact is predominantly in the distal airways. The majority of documented test preparations study acute secretion, invariably using tracheal preparations, but have been invaluable in elucidating the normal physiology of airway mucus secretion. Chronic models of the hypersecretory state in the distal airways have been developed, but are predominantly histologic in nature (for example quantification of increased goblet cell number). There are few investigations of mucus hypersecretion. Examination of the 'antisecretory' potential of pharmaceutical compounds has been investigated predominantly in chronic histologic models with the drug being given 'prophylactically' rather than 'therapeutically'. Refinement of chronic hypersecretory models should lead to elucidation of the connection between airway irritation, inflammation, MUC gene expression, mucous cell hyperplasia/metaplasia, airway hypersecretion and bronchial hypersecretory disease.