ABSTRACT
Genome packaging is a fundamental process in a viral life cycle and a prime target of antiviral drugs. Herpesviruses use an ATP-driven packaging motor/terminase complex to translocate and cleave concatemeric dsDNA into procapsids but its molecular architecture and mechanism are unknown. We report atomic structures of a herpesvirus hexameric terminase complex in both the apo and ADP•BeF3-bound states. Each subunit of the hexameric ring comprises three components-the ATPase/terminase pUL15 and two regulator/fixer proteins, pUL28 and pUL33-unlike bacteriophage terminases. Distal to the nuclease domains, six ATPase domains form a central channel with conserved basic-patches conducive to DNA binding and trans-acting arginine fingers are essential to ATP hydrolysis and sequential DNA translocation. Rearrangement of the nuclease domains mediated by regulatory domains converts DNA translocation mode to cleavage mode. Our structures favor a sequential revolution model for DNA translocation and suggest mechanisms for concerted domain rearrangements leading to DNA cleavage.
ABSTRACT
Genome packaging is a fundamental process in a viral life cycle and a prime target of antiviral drugs. Herpesviruses use an ATP-driven packaging motor/terminase complex to translocate and cleave concatemeric dsDNA into procapsids but its molecular architecture and mechanism are unknown. We report atomic structures of a herpesvirus hexameric terminase complex in both the apo and ADP•BeF3-bound states. Each subunit of the hexameric ring comprises three components-the ATPase/terminase pUL15 and two regulator/fixer proteins, pUL28 and pUL33-unlike bacteriophage terminases. Distal to the nuclease domains, six ATPase domains form a central channel with conserved basic-patches conducive to DNA binding and trans-acting arginine fingers are essential to ATP hydrolysis and sequential DNA translocation. Rearrangement of the nuclease domains mediated by regulatory domains converts DNA translocation mode to cleavage mode. Our structures favor a sequential revolution model for DNA translocation and suggest mechanisms for concerted domain rearrangements leading to DNA cleavage.
ABSTRACT
Objective To investigate the effect of sodium houttuyfonate on the expression of PI3K and AKT1 and mTOR mRNA in the lung of rats with chronic obstructive pulmonary disease(COPD),and reveal the possible mechanism of the COPD treated with sodium houttuyfonate. Methods Twenty-four male Wistar rats were randomly divided into normal control group,model control group,dexamethasone group and sodium houttuyfonate group(n=6 for each). The rat models of COPD were established by intratracheal instillation of lipopolysaccharide and smudging. The expressions of PI3K and AKT1 and mTOR mRNA were determined by real-time PCR. The morphological changes of the lung tissue was examined by histopathology. Results Compared with the normal control group,the expressions of PI3K and AKT1 were significantly in-creased and mTOR mRNA was significantly decreased in the model group(P<0.01,P<0.05). Compared with the mod-el group,the expressions of PI3K and AKT1 were significantly decreased and mTOR mRNA was significantly increased in the sodium houttuyfonate group and dexamethasone group(P<0.01,P<0.05). Compared with the dexamethasone group, the expression of mTOR mRNA was significantly increased in the sodium houttuyfonate group(P<0.05). The pathological observation indicated that there were local pulmonary consolidation and a extensive neutrophil infiltration in the alveolar cav-ity. Prominent pulmonary interstitial fibrous hyperplasia was observed in the model group. The pathological manifestations were much ameliorated than those of the model group,and only mild interstitial pneumonia and a slight fibrous hyperplasia were seen in the sodium houttuyfonate and the dexamethasone groups. Conclusions Sodium houttuyfonate reduces the in-jury of lung tissue and has protective effect on COPD rats. The mechanism is probably related to the down-regulatation of expression of PI3K and AKT1 mRNA and up-regulatation of expression of mTOR mRNA in COPD rats.