HIV-1 protease and reverse transcriptase control the architecture of their nucleocapsid partner.

The HIV-1 nucleocapsid is formed during protease (PR)-directed viral maturation, and is transformed into pre-integration complexes following reverse transcription in the cytoplasm of the infected cell. Here, we report a detailed transmission electron microscopy analysis of the impact of HIV-1 PR and reverse transcriptase (RT) on nucleocapsid plasticity, using in vitro reconstitutions. After binding to nucleic acids, NCp15, a proteolytic intermediate of nucleocapsid protein (NC), was processed at its C-terminus by PR, yielding premature NC (NCp9) followed by mature NC (NCp7), through the consecutive removal of p6 and p1. This allowed NC co-aggregation with its single-stranded nucleic-acid substrate. Examination of these co-aggregates for the ability of RT to catalyse reverse transcription showed an effective synthesis of double-stranded DNA that, remarkably, escaped from the aggregates more efficiently with NCp7 than with NCp9. These data offer a compelling explanation for results from previous virological studies that focused on i) Gag processing leading to nucleocapsid condensation, and ii) the disappearance of NCp7 from the HIV-1 pre-integration complexes. We propose that HIV-1 PR and RT, by controlling the nucleocapsid architecture during the steps of condensation and dismantling, engage in a successive nucleoprotein-remodelling process that spatiotemporally coordinates the pre-integration steps of HIV-1. Finally we suggest that nucleoprotein remodelling mechanisms are common features developed by mobile genetic elements to ensure successful replication.

Reduction of left ventricular hypertrophy in children undergoing hemodialysis.

Left ventricular hypertrophy (LVH) is related to a 1,000-fold increased risk of cardiovascular morbidity and mortality in young adults with end-stage renal disease (ESRD) treated with hemodialysis (HD) or peritoneal dialysis. We report a series of 17 children (5 girls, 12 boys), with a median (range) age of 11 (2-18) years, all treated by HD, who presented with an increased left ventricular mass (LVM) index of 54.8+/-4.5 g/m2.7 at onset of HD and reached 36.2+/-2.6 g/m2.7 (mean+/-SEM, P<0.0001) at last follow up. Over the observation period, systolic (P<0.0001) and diastolic (P<0.0001) blood pressure (indexed for height, gender, and age) decreased and hemoglobin (+2.8 g/dL; P<0.0001) increased compared to initial values. Only BP as well as plasma protein level at onset of HD session correlated with LVM in multiple correlation analysis. In conclusion, increased LVM is a common feature in pediatric patients with ESRD. Normalization of BP and reduction of the extracellular volume (represented by plasma protein at onset of HD session) are key points in reducing LVH during HD in children.

Overexpression of beta2-adrenergic receptors in mouse liver alters the expression of gluconeogenic and glycolytic enzymes.

In the livers of humans and many other mammalian species, beta2-adrenergic receptors (beta2-ARs) play an important role in the modulation of glucose production by glycogenolysis and gluconeogenesis. In male mice and rats, however, the expression and physiological role of hepatic beta2-ARs are rapidly lost with development under normal physiological conditions. We previously described a line of transgenic mice, F28 (Andre C, Erraji L, Gaston J, Grimber G, Briand P, and Guillet JG. Eur J Biochem 241: 417-424, 1996), which carry the human beta2-AR gene under the control of its own promoter. In these mice, hepatic beta2-AR levels are shown to increase rapidly after birth and, as in humans, be maintained at an elevated level in adulthood. F28 mice display strongly enhanced adenylyl cyclase responses to beta-AR agonists in their livers and, compared with normal mice, have increased basal hepatic adenylyl cyclase activity. In this report we demonstrate that, under normal physiological conditions, this increased beta2-AR activity affects the expression of the gluconeogenic and glycolytic key enzymes phosphoenolpyruvate carboxykinase, glucose-6-phosphatase, and l-pyruvate kinase and considerably decreases hepatic glycogen levels. Furthermore, we show that the effects of beta-adrenergic ligands on liver glycogen observed in humans are reproduced in these mice: liver glycogen levels are strongly decreased by the beta2-AR agonist clenbuterol and increased by the beta-AR antagonist propranolol. These transgenic mice open new perspectives for studying in vivo the hepatic beta2-AR system physiopathology and for testing the effects of beta-AR ligands on liver metabolism.

Burkholderia cepacia is associated with pulmonary hypertension and increased mortality among cystic fibrosis patients.

The aim of the study was to evaluate the impact of Burkholderia cepacia on cardiovascular status and mortality in cystic fibrosis. Seven patients infected with B. cepacia were matched with 31 patients not infected with this organism for gender, age, height, weight, genotype, and percent predicted forced expiratory volume in one second, partial arterial oxygen pressure, and pancreatic sufficiency status. The pulmonary artery systolic pressure, as assessed by transthoracic echocardiography, was significantly higher in patients infected with B. cepacia (61.3 +/- 17.2 mm Hg) than in controls (37.3 +/- 13.9 mm Hg; P = 0.02), and the mean acceleration time was significantly lower (77 +/- 33 ms versus 108 +/- 25 ms; P = 0.02). The 6-month mortality was significantly higher in patients infected with B. cepacia (57% versus 16%; P = 0.02). Six of the seven patients infected with B. cepacia harbored the same ribotype (genomovar II, B. multivorans). Pulmonary hypertension was significantly more frequent in patients infected by B. cepacia and could contribute to the increased mortality rate.