S Choe

The Vpr accessory gene product of human immunodeficiency virus types 1 and 2 and simian immunodeficiency virus is believed to play a role in permitting entry of the viral core into the nucleus of nondividing cells. A second role for Vpr was recently suggested by Rogel et al. (M. E. Rogel, L. I. Wu, and M. Emerman, J. Virol. 69:882-888, 1995), who showed that Vpr prevents the establishment in vitro of chronically infected HIV producer cell lines, apparently by causing infected cells to arrest in the G2/M phase of the cell cycle. In cycling cells, progression from G2 to M phase is driven by activation of the p34cdc2/cyclin B complex, an event caused, in part, by dephosphorylation of two regulatory amino acids of p34cdc2 (Thr-14 and Tyr-15). We show here that Vpr arrests the cell cycle in G2 by preventing the activation of the p34cdc2/cyclin B complex. Vpr expression in cells caused p34cdc2 to remain in the phosphorylated, inactive state, p34cdc2/cyclin B complexes immunoprecipitated from cells expressing Vpr were almost completely inactive in a histone H1 kinase assay. Coexpression of a constitutively active mutant p34cdc2 molecule with Vpr relieved the G2 arrest. These findings strongly suggest that Vpr arrests cells in G2 by preventing the activation of the p34cdc2/cyclin B complex that is required for entry into M phase. In vivo, Vpr might, by preventing p34cdc2 activation, delay or prevent apoptosis of infected cells. This would increase the amount of virus each infected cell produced.

Human immunodeficiency virus type 1 Vpr is a virion-associated, regulatory protein that is required for efficient viral replication in monocytes/macrophages. The protein is believed to act in conjunction with the Gag matrix protein to allow import of the viral preintegration complex in nondividing cells. In cells, Vpr localizes to the nucleus. Recently, we showed that Vpr prevents the activation of p34cdc2-cyclin B. This results in arrest of Vpr-expressing cells in the G2/M phase of the cell cycle. Here, we use a panel of expression vectors encoding Vpr molecules mutated in the amino-terminal alpha-helical region, the central hydrophobic region, or the carboxy-terminal basic region to define the functional domains of the protein. The results showed cell cycle arrest was largely controlled by the carboxy-terminal basic domain of the protein. In contrast, the amino-terminal alpha-helical region of Vpr was required for nuclear localization and packaging into virions. The carboxy terminus appeared to be unnecessary for nuclear localization. In the alpha-helical region, mutation of Ala-30 to Pro resulted in a protein that localized to the cytoplasm. Surprisingly, fusion of Vpr to luciferase resulted in a molecule that failed to localize to the nucleus. In addition, we show that simian immunodeficiency virus Vpr, but not Vpx, induces G2 arrest. We speculate that Vpr has two sites for interaction with cellular factors: one in the alpha-helical region that specifies nuclear localization and one in the carboxy-terminal domain that is required for Cdc2 inhibition.

상산나무 잎의 항미생물 활성을 알아보기 위하여 상산나무 잎을 메탄올, 70% 에탄올, <TEX>$65^{\circ}C$</TEX> 열수로 추출하였고 각각의 추출물에 대하여 13종의 미생물에 대하여 항미생물 활성을 paper disc diffusion법으로 측정하였다. 그 결과 4개 균주 S. mutans, B. cereus, S. aureus, P. aeruginosa가 메탄올 추출물, 70% 에탄올 추출물에서 clear zone을 형성하여 추출물에 의하여 생육이 저해되는 것을 확인할 수 있었고 methanol 추출물이 70% ethanol 추출물에 비하여 항균활성이 크게 나타났다. 이에 methanol 추출물을 극성이 다른 여러 용매로 분획추출하고 항균활성을 측정한 결과 dichloromethane 분획물에서 항균활성을 나타냈으며 다른 분획물인 n-hexane, ethyl acetate, butanol, water 분획물에서는 항균활성이 나타나지 않았다. 가장 활성이 크게 나타났던 메탄올 추출물의 항균활성을 보인 4개의 균에 대하여 최소저해농도를 측정한 결과 S. mutans, S. aureus, P. aeruginosa는 추출물의 농도가 49.22 mg/mL에서 항균활성이 나타났으며 B. cereus의 경우 24.61 mg/mL에서 항균활성을 나타내었으며 S. mutans, B. cereus, S. aureus, P. aeruginosa에 대한 dichloromethane 분획물의 최소저해농도는 각각 3.31, 0.21, 1.7, 1.7 mg/mL으로 나타났다. 메탄올 추출물의 pH에 대한 안정성을 알아보기 위하여 pH 3, 7, 11로 조절하여 1-3시간 동안 처리한 결과 항균활성에는 영향을 주지 않았고 열에 대한 안정성을 확인하기 위하여 80, <TEX>$100^{\circ}C$</TEX>에서 1-6시간 동안 처리한 결과 대조군과 차이가 없었고 <TEX>$120^{\circ}C$</TEX> 처리한 경우 항균활성이 약간 저하되었으나 항균활성이 완전히 실활 되지 않은 것으로 보아 상산나무 잎 methanol 추출물은 열과 pH에 비교적 안정하여 식품의 가공 처리에도 적합한 천연 식품첨가물로 유용하게 이용될 수 있을 것으로 사료된다. The antimicrobial activity of Orixa japonica Thunb. leaf extract towards 13 microorganism strains was evaluated. Both methanol (MEex) and 70% ethanol extracts showed antimicrobial activity towards Streptococcus mutans, Bacillus cereus, Staphylococcus aureus, and Pseudomonas aeruginosa. MEex showed a higher antimicrobial activity than the 70% ethanol extract. In addition, the dichloromethane fraction (DCMfr) of the MEex also had an antimicrobial effect against the microorganisms examined. The minimum inhibitory concentrations (MICs) towards S. mutans, B. cereus, S. aureus, and P. aeruginosa were 49.22, 24.61, 49.22, and 49.22 mg/mL, respectively. In contrast, the MICs of the DCMfr tpwards S. mutans, B. cereus, S. aureus, and P. aeruginosa were 3.31, 0.21, 1.7, and 1.7 mg/mL, respectively. The MEex antimicrobial activity was not affected by a 3 h exposures to pH in the range of 3-11 or by temperatures were maintained between <TEX>$80^{\circ}C-100^{\circ}C$</TEX> for 6 h. However, the MEex antimicrobial activity decreased at a heat treatment of <TEX>$121^{\circ}C$</TEX> 1 h.