Ebolavirus Replication and Tetherin/BST-2

Ebolavirus (EBOV) is an enveloped, non-segmented, negative-stranded RNA virus, which consists of five species: Zaire ebolavirus, Sudan ebolavirus, Tai Forest ebolavirus, Bundibugyo ebolavirus, and Reston ebolavirus. EBOV causes a lethal hemorrhagic fever in both humans and non-human primates. The EBOV RNA genome encodes seven viral proteins: NP, VP35, VP40, GP, VP30, VP24, and L. VP40 is a matrix protein and is essential for virus assembly and release from host cells. Expression of VP40 in mammalian cells is sufficient to generate extracellular virus-like particles, which resemble authentic virions. Tetherin/BST-2, which was identified as an effective cellular factor that prevents human immunodeficiency virus-1 release in the absence of viral accessory protein Vpu, has been reported to inhibit ZEBOV VP40-induced VLP release. Tetherin/BST-2 appears to inhibit virus release by physically tethering viral particles to the cell surface via its N-terminal transmembrane domain and C-terminal glycosylphosphatidylinositol anchor. Replication of ZEBOV is not inhibited by tetherin/BST-2 expression, although tetherin/BST-2 was expected to inhibit EBOV release as well as VLP release. Recently, it was reported that viral glycoprotein of EBOV, GP, antagonizes the antiviral effect of tetherin/BST-2. However, the mechanism by which GP antagonizes the antiviral activity of tetherin/BST-2 and whether GP of the other EBOV species function as antagonists of tetherin/BST-2 remain unclear

Regulation of HTLV-1 Gag budding by Vps4A, Vps4B, and AIP1/Alix

<p>Abstract</p> <p>Background</p> <p>HTLV-1 Gag protein is a matrix protein that contains the PTAP and PPPY sequences as L-domain motifs and which can be released from mammalian cells in the form of virus-like particles (VLPs). The cellular factors Tsg101 and Nedd4.1 interact with PTAP and PPPY, respectively, within the HTLV-1 Gag polyprotein. Tsg101 forms a complex with Vps28 and Vps37 (ESCRT-I complex) and plays an important role in the class E Vps pathway, which mediates protein sorting and invagination of vesicles into multivesicular bodies. Nedd4.1 is an E3 ubiquitin ligase that binds to the PPPY motif through its WW motif, but its function is still unknown. In the present study, to investigate the mechanism of HTLV-1 budding in detail, we analyzed HTLV-1 budding using dominant negative (DN) forms of the class E proteins.</p> <p>Results</p> <p>Here, we report that DN forms of Vps4A, Vps4B, and AIP1 inhibit HTLV-1 budding.</p> <p>Conclusion</p> <p>These findings suggest that HTLV-1 budding utilizes the MVB pathway and that these class E proteins may be targets for prevention of mother-to-infant vertical transmission of the virus.</p

Roles of the three L-domains in β-retrovirus budding

Retroviral Gag protein plays a critical role during the late stage of virus budding and possesses a so-called L-domain containing PT/SAP, PPxY, YxxL or FPIV motifs that are critical for efficient budding. Mason-Pfizer monkey virus (M-PMV) contains PSAP, PPPY, and YADL sequences in Gag. This study was performed to investigate the roles of these three L-domain-like sequences in virus replication in three different cell lines, 293T, COS-7 and HeLa cells. It was found that the PPxY motif plays an essential role in progeny virus production as a major L-domain in all three cell lines. The PSAP sequence was shown to function as an additional L-domain in HeLa cells and to promote efficient release of M-PMV; however, this sequence was dispensable for M-PMV production in 293T and COS-7 cells, suggesting that the role of the PSAP motif as an L-domain in M-PMV budding is cell type-dependent. Viruses possessing multiple L-domains appear to change the L-domain usage to replicate in various cells. On the other hand, the YADL motif was required for M-PMV production as a transport signal of Gag to the plasma membrane, but not as an L-domain

Effect of day length on growth and flowering of gladiolus. : 2. Effect of day length of 10 and 11 hours in summer.

1)グラジオラスの開花が日照時間を冬の最少日照時間と同じ即ち10～11時間に制限した場合如何なる影響を受けるかについて試験をした.供試品種はヘクター,ストップライト,ラジアンスの3品種で,これらを使つて標準区と比較した. 2)10及び11日照時間区は標準区に比し,何れも幾分開花期が早くなるが,ブラインドの現われる率も高くなる. 3)10及び11日照時間区の草丈,葉数及び着花数は標準区より幾分減少するが,その差は僅かである. 4)グラジオラスの開花に必要な日照時間は夏季に於て9時間では不足で,少くとも10～11時間を必要とする.但し,これは品種に依て差があるようである. 5)以上の結果から推して,グラジオラスの冬季開花には温度の他,日照時間以外の要素例えば日照の強さ,日射量などが関係しているように思われる.何故ならば,グラジオラスは日照時間の短い冬にはたとえ温度を高めてもブラインドの発生が極めて多いからである