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Macroautophagy is an intracellular degradation system that involves the de novo formation of membrane structures called autophagosomes, although the detailed process by which membrane lipids are supplied during autophagosome formation is yet to be elucidated. Macroautophagy is thought to be associated with canonical membrane trafficking, but several mechanistic details are still missing. In this review, the current understanding and potential mechanisms by which membrane trafficking participates in macroautophagy are described, with a focus on the enigma of the membrane protein Atg9, for which the proximal mechanisms determining its movement are disputable, despite its key role in autophagosome formation. [ABSTRACT FROM AUTHOR]

Autophagy is an intracellular protein-degradation process that is conserved across eukaryotes including yeast and humans. Under nutrient starvation conditions, intracellular proteins are transported to lysosomes and vacuoles via membranous structures known as autophagosomes, and are degraded. The various steps of autophagy are regulated by the target of rapamycin complex 1 (TORC1/mTORC1). In this review, a history of this regulation and recent advances in such regulation both in yeast and mammals will be discussed. Recently, the mechanism of autophagy initiation in yeast has been deduced. The autophagy-related gene 13 (Atg13) and the unc-51 like autophagy activating kinase 1 (Ulk1) are the most crucial substrates of TORC1 in autophagy, and by its dephosphorylation, autophagosome formation is initiated. Phosphorylation/dephosphorylation of Atg13 is regulated spatially inside the cell. Another TORC1-dependent regulation lies in the expression of autophagy genes and vacuolar/lysosomal hydrolases. Several transcriptional and post-transcriptional regulations are controlled by TORC1, which affects autophagy activity in yeast and mammals. [ABSTRACT FROM AUTHOR]

We observe lateral currents induced in an n-AlGaAs/GaAs heterojunction channel of Hall bar geometry, when an asymmetric position of the Schottky metal gate is locally irradiated by a near-infrared laser beam. When the left side of the Schottky gate is illuminated with the laser, the lateral current flows from left to right in the two dimensional electron gas (2DEG) channel. In contrast, the right side illumination leads to the current from right to left. The magnitude of the lateral current is almost linearly dependent on the beam position, the current reaching its maximum for the beam at the edge of the Schottky gate. The experimental findings are well explained by a theory based on the current-continuity equation, where the lateral current in the 2DEG channel is driven by the photocurrent which vertically flows from the 2DEG to the Schottky gate. [ABSTRACT FROM AUTHOR]

Ebola virus (EBOV) VP24, together with nucleoprotein and VP35, is an essential component of viral RNA-protein complexes called "nucleocapsids." In this study, using a series of deletion mutants of VP24, we identified regions within VP24 that are important for the formation of nucleocapsid-like structures and determined that both termini of VP24 are essential for nucleocapsid formation. This finding advances our knowledge of both EBOV morphogenesis and the nature of VP24 molecules in nucleocapsid formation, which will be useful for the development of antiviral compounds. [ABSTRACT FROM AUTHOR]

The surface diffusion of In atoms from an In droplet and their subsequent reaction with As4molecules lead to the formation of InAs quantum dots elliptically distributed around the initially formed droplet. The size of this elliptic dot cluster depends sensitively on the growth conditions. For instance, as the substrate temperature Tsis raised from 220 to 350 °C, the shorter and longer diameters of the elliptic clusters, elongated in the [011] direction, increase exponentially with Ts, expanding from the range of 0.8−1.6 μm to 2−7 μm. When the pressure PAsof As4is increased from 0.7 to 10 × 10−5Torr at Ts= 300 °C, the cluster diameters shrink from 3−6 μm to 1−2 μm in inverse proportion to PAs0.3−0.4. These findings are interpreted in terms of anisotropic diffusion of In atoms from the droplet. [ABSTRACT FROM AUTHOR]

Lassa virus (LASV) is the causative agent of human Lassa fever which in severe cases manifests as hemorrhagic fever leading to thousands of deaths annually. However, no approved vaccines or antiviral drugs are currently available. Recently, we screened approximately 2,500 compounds using a recombinant vesicular stomatitis virus (VSV) expressing LASV glycoprotein GP (VSV-LASVGP) and identified a P-glycoprotein inhibitor as a potential LASV entry inhibitor. Here, we show that another identified candidate, hexestrol (HES), an estrogen receptor agonist, is also a LASV entry inhibitor. HES inhibited VSV-LASVGP replication with a 50% inhibitory concentration (IC50) of 0.63 µM. Importantly, HES also inhibited authentic LASV replication with IC50 values of 0.31 µM–0.61 µM. Time-of-addition and cell-based membrane fusion assays suggested that HES inhibits the membrane fusion step during virus entry. Alternative estrogen receptor agonists did not inhibit VSV-LASVGP replication, suggesting that the estrogen receptor itself is unlikely to be involved in the antiviral activity of HES. Generation of a HES-resistant mutant revealed that the phenylalanine at amino acid position 446 (F446) of LASVGP, which is located in the transmembrane region, conferred resistance to HES. Although mutation of F446 enhanced the membrane fusion activity of LASVGP, it exhibited reduced VSV-LASVGP replication, most likely due to the instability of the pre-fusion state of LASVGP. Collectively, our results demonstrated that HES is a promising anti-LASV drug that acts by inhibiting the membrane fusion step of LASV entry. This study also highlights the importance of the LASVGP transmembrane region as a target for anti-LASV drugs. IMPORTANCE Lassa virus (LASV), the causative agent of Lassa fever, is the most devastating mammarenavirus with respect to its impact on public health in West Africa. However, no approved antiviral drugs or vaccines are currently available. Here, we identified hexestrol (HES), an estrogen receptor agonist, as the potential antiviral candidate drug. We showed that the estrogen receptor itself is not involved in the antiviral activity. HES directly bound to LASVGP and blocked membrane fusion, thereby inhibiting LASV infection. Through the generation of a HES-resistant virus, we found that phenylalanine at position 446 (F446) within the LASVGP transmembrane region plays a crucial role in the antiviral activity of HES. The mutation at F446 caused reduced virus replication, likely due to the instability of the pre-fusion state of LASVGP. These findings highlight the potential of HES as a promising candidate for the development of antiviral compounds targeting LASV. [ABSTRACT FROM AUTHOR]

Both the biogenesis and functions of osteoclasts and macrophages involves dynamic membrane traffic. We screened transcript levels for Rab family small GTPases related to osteoclasts and identified Rab38. Rab38 expression is upregulated during osteoclast differentiation and maturation. In osteoclasts, both Rab38 and its paralog, Rab32, colocalize to lysosome-related organelles (LROs). In macrophages, Rab32 is also found in LROs. LROs are part of the endocytic pathway but are distinct from lysosomes. After receptor activator of NF-κB ligand stimulation, LROs contain cathepsin K and tartrateresistant acid phosphatase inside and help both proteins to accumulate around bone resorption pits. After osteoclast maturation, these enzymes are hardly found within LROs. In macrophages derived from Rab32 and Rab38 double knockout mice, both acidification and V-ATPase a3 localization were severely compromised. Both the double knockout macrophage and bafilomycin-treated wildtype macrophage show an increase in Lamp1-positive organelles, implying that biogenesis of lysosomes and LROs are related. These results indicate that Rab32 and Rab38 both play a crucial role in LRO biogenesis in macrophages and in osteoclasts. [ABSTRACT FROM AUTHOR]

Ebola virus (EBOV) VP30 regulates viral genome transcription and replication by switching its phosphorylation status. However, the importance of VP30 phosphorylation and dephosphorylation in other viral replication processes such as nucleocapsid and virion assembly is unclear. Interestingly, VP30 is predominantly dephosphorylated by cellular phosphatases in viral inclusions, while it is phosphorylated in the released virions. Thus, uncertainties regarding how VP30 phosphorylation in nucleocapsids is achieved and whether VP30 phosphorylation provides any advantages in later steps in viral replication have arisen. In the present study, to characterize the roles of VP30 phosphorylation in nucleocapsid formation, we used electron microscopic analyses and live cell imaging systems. We identified VP30 localized to the surface of protrusions surrounding nucleoprotein (NP)- forming helical structures in the nucleocapsid, suggesting the involvement in assembly and transport of nucleocapsids. Interestingly, VP30 phosphorylation facilitated its association with nucleocapsid-like structures (NCLSs). On the contrary, VP30 phosphorylation does not influence the transport characteristics and NCLS number leaving from and coming back into viral inclusions, indicating that the phosphorylation status of VP30 is not a prerequisite for NCLS departure. Moreover, the phosphorylation status of VP30 did not cause major differences in nucleocapsid transport in authentic EBOV-infected cells. In the following budding step, the association of VP30 and its phosphorylation status did not influence the budding efficiency of virus-like particles. Taken together, it is plausible that EBOV may utilize the phosphorylation of VP30 for its selective association with nucleocapsids, without affecting nucleocapsid transport and virion budding processes. [ABSTRACT FROM AUTHOR]

In measles virus (MV)-infected cells, the ribonucleoprotein (RNP) complex, comprised of the viral genome and the nucleocapsid (N) protein, phosphoprotein (P protein), and large protein, assembles at the perinuclear region and synthesizes viral RNAs. The cellular proteins involved in the formation of the RNP complex are largely unknown. In this report, we show that cofilin, an actin-modulating host protein, interacts with the MV N protein and aids in the formation of the RNP complex. Knockdown of cofilin using the short hairpin RNA reduces the formation of the RNP complex after MV infection and that of the RNP complex-like structure after plasmid-mediated expression of MV N and P proteins. A lower level of formation of the RNP complex results in the reduction of viral RNA synthesis. Cofilin phosphorylation on the serine residue at position 3, an enzymatically inactive form, is increased after MV infection and the phosphorylated form of cofilin is preferentially included in the complex. These results indicate that cofilin plays an important role in MV replication by increasing formation of the RNP complex and viral RNA synthesis. [ABSTRACT FROM AUTHOR]

The influenza A virus possesses an eight-segmented, negative-sense, single-stranded RNA genome (vRNA). Each vRNA segment binds to multiple copies of viral nucleoproteins and a small number of heterotrimeric polymerase complexes to form a rod-like ribonucleoprotein complex (RNP), which is essential for the transcription and replication of the vRNAs. However, how the RNPs are organized within the progeny virion is not fully understood. Here, by focusing on polymerase complexes, we analyzed the fine structure of purified RNPs and their configuration within virions by using various electron microscopies (EM). We confirmed that the individual RNPs possess a single polymerase complex at one end of the rod-like structure and that, as determined using immune EM, some RNPs are incorporated into budding virions with their polymerase-binding ends at the budding tip, whereas others align with their polymerase-binding ends at the bottom of the virion. These data further our understanding of influenza virus virion morphogenesis. [ABSTRACT FROM AUTHOR]

The influenza A virus genome is composed of eight single-stranded negative-sense viral RNA segments (vRNAs). The eight vRNAs are selectively packaged into each progeny virion. This process likely involves specific interactions between the vRNAs via segment-specific packaging signals located in both the 39- and 59-terminal regions of the respective vRNAs. To assess the importance of vRNAvRNA interactions via packaging signals for selective genome packaging, we generated mutant viruses possessing silent mutations in the packaging signal region of the hemagglutinin (HA) vRNA. A mutant virus possessing silent mutations in nucleotides (nt) 1664 to 1676 resulted in defects in HA vRNA incorporation and showed a reduction in viral growth. After serial passage, the mutant virus acquired additional mutations in the 59-terminal packaging signal regions of both the HA and polymerase basic 2 (PB2) vRNAs. These mutations contributed to the recovery of viral growth and HA vRNA packaging efficiency. In addition, an RNA-RNA interaction between the 59 ends of HA and PB2 vRNAs was confirmed in vitro, and this interaction was disrupted following the introduction of silent mutations in the HA vRNA. Thus, our results demonstrated that RNA-RNA interactions between the packaging signal regions of HA vRNA and PB2 vRNA are important for selective genome packaging. [ABSTRACT FROM AUTHOR]

The influenza A virus genome comprises eight single-stranded negative-sense RNA segments (vRNAs). All eight vRNAs are selectively packaged into each progeny virion via so-called segment-specific genome-packaging signal sequences that are located in the noncoding and terminal coding regions of both the 3' and the 5' ends of the vRNAs. However, it remains unclear how these signals ensure that eight different vRNAs are packaged. Here, by using a reverse genetics system, we demonstrated that, in the absence of the other seven vRNAs, a recombinant NP vRNA bearing only a reporter gene flanked by the noncoding NP regions was incorporated into virus-like particles (VLPs) as efficiently as a recombinant NP vRNA bearing the reporter gene flanked by the complete NP packaging signals (i.e., the noncoding sequences and the terminal coding regions). Viruses that comprised a recombinant NP vRNA whose packaging signal was disrupted, and the remaining seven authentic vRNAs, did not undergo multiple cycles of replication; however, a recombinant NP vRNA with only the noncoding regions was readily incorporated into VLPs, suggesting that the packaging signal as currently defined is not necessarily essential for the packaging of the vRNA in which it resides; rather, it is required for the packaging of the full set of vRNAs. We propose that the 3' and 5' noncoding regions of each vRNA bear a virion incorporation signal for that vRNA and that the terminal coding regions serve as a bundling signal that ensures the incorporation of the complete set of eight vRNAs into the virion. [ABSTRACT FROM AUTHOR]

An RNA virus-based episomal vector (REVec) whose backbone is Borna disease virus 1 (BoDV-1) can provide long-term gene expression in transduced cells. To improve the transduction efficiency of REVec, we evaluated the role of the viral envelope glycoprotein (G) of the genus Orthobornavirus, including that of BoDV-1, in the production of infectious particles. By using a G-pseudotype assay in which the lack of G in G-deficient REVec (DG-REVec) was compensated for the expression of G, we found that excess expression of BoDV-1-G does not affect particle production itself but results in uncleaved and aberrant mature G expression in the cells, leading to the production of REVec particles with low transduction titers. We revealed that the expression of uncleaved G in the cells inhibits the incorporation of mature G and viral genomic RNA into the particles. This feature of G was conserved among mammalian and avian orthobornaviruses; however, the cleavage efficacy of canary bornavirus 1 (CnBV-1)-G was exceptionally not impaired by its excess expression, which led to the production of the pseudotype ΔG-REVec with the highest titer. Chimeric G proteins between CnBV-1 and -2 revealed that the signal peptide of CnBV-1-G was responsible for the cleavage efficacy through the interaction with intracellular furin. We showed that CnBV-1-G leads to the development of pseudotyped REVec with high transduction efficiency and a high-titer recombinant REVec. Our study demonstrated that the restricted expression of orthobornavirus G contributes to the regulation of infectious particle production, the mechanism of which can improve the transduction efficiency of REVec. IMPORTANCE Most viruses causing persistent infection produce few infectious particles from the infected cells. Borna disease virus 1, a member of the genus Orthobornavirus, is an RNA virus that persistently infects the nucleus and has been applied to vectors for long-term gene expression. In this study, we showed that, common among orthobornaviruses, excessive G expression does not affect particle production itself but reduces the production of infectious particles with mature G and genomic RNA. This result suggested that limited G expression contributes to suppressing abnormal viral particle production. On the other hand, we found that canary bornavirus 1 has an exceptional G maturation mechanism and produces a high-titer virus. Our study will contribute to not only understanding the mechanism of infectious particle production but also improving the vector system of orthobornaviruses. [ABSTRACT FROM AUTHOR]

In macroautophagy, membrane structures called autophagosomes engulf substrates and deliver them for lysosomal degradation. Autophagosomes enwrap a variety of targets with diverse sizes, from portions of cytosol to larger organelles. However, the mechanism by which autophagosome size is controlled remains elusive. We characterized a novel ER membrane protein, ERdj8, in mammalian cells. ERdj8 localizes to a meshwork-like ER subdomain along with phosphatidylinositol synthase (PIS) and autophagy-related (Atg) proteins. ERdj8 overexpression extended the size of the autophagosome through its DnaJ and TRX domains. ERdj8 ablation resulted in a defect in engulfing larger targets. C. elegans, in which the ERdj8 orthologue dnj-8 was knocked down, could perform autophagy on smaller mitochondria derived from the paternal lineage but not the somatic mitochondria. Thus, ERdj8 may play a critical role in autophagosome formation by providing the capacity to target substrates of diverse sizes for degradation. [ABSTRACT FROM AUTHOR]

While it is well appreciated that late domains in the viral matrix proteins are crucial to mediate efficient virus budding, little is known about roles of late domains in the viral nucleocapsid proteins. Here, we characterized the functional relevance of a YxxL motif with potential late domain function in the Ebola virus nucleocapsid protein VP24. Mutations in the YxxL motif had two opposing effects on the functions of VP24. On the one hand the mutation affected the regulatory function of VP24 in viral RNA transcription and replication, which correlated with an increased incorporation of minigenomes into released transcription- and replication-competent virus-like particles (trVLPs). Consequently, cells infected with those trVLPs showed higher levels of viral transcription. On the other hand, mutations of the YxxL motif greatly impaired the intracellular transport of nucleocapsid-like structures (NCLSs) composed of the viral proteins NP, VP35 and VP24 and the length of released trVLPs. Attempts to rescue recombinant Ebola virus expressing YxxL-deficient VP24 failed, underlining the importance of this motif for the viral life cycle. [ABSTRACT FROM AUTHOR]

The article offers information on the role of osteoblastic lysosome in mineralization, which is the most fundamental process in vertebrates. Topics discussed include its mediation by osteoblasts, which secrete mineral precursors, most likely through matrix vesicles (MVs); the MVs that are calcium and phosphate rich and contain organic material such as acidic proteins; and transportation and secretion of intracellular MVs.

Histone acetylation plays crucial roles in transcriptional regulation and chromatin organization. Viral RNA of the influenza virus interacts with its nucleoprotein (NP), whose function corresponds to that of eukaryotic histones. NP regulates viral replication and has been shown to undergo acetylation by the cAMP-response element (CRE)-binding protein (CBP) from the host. However, whether NP is the target of other host acetyltransferases is unknown. Here, we show that influenza virus NP undergoes acetylation by the two host acetyltransferases GCN5 and P300/CBP-associated factor (PCAF) and that this modification affects viral polymerase activities. Western blot analysis with anti-acetyl-lysine antibody on cultured A549 human lung adenocarcinoma epithelial cells infected with different influenza virus strains indicated acetylation of the viral NP. A series of biochemical analyses disclosed that the host lysine acetyltransferases GCN5 and PCAF acetylate NP in vitro. MS experiments identified three lysine residues as acetylation targets in the host cells and suggested that Lys-31 and Lys-90 are acetylated by PCAF and GCN5, respectively. RNAi-mediated silencing of GCN5 and PCAF did not change acetylation levels of NP. However, interestingly, viral polymerase activities were increased by the PCAF silencing and were decreased by the GCN5 silencing, suggesting that acetylation of the Lys-31 and Lys-90 residues has opposing effects on viral replication. Our findings suggest that epigenetic control of NP via acetylation by host acetyltransferases contributes to regulation of polymerase activity in the influenza A virus. [ABSTRACT FROM AUTHOR]

Exosomes regulate cell-cell communication by transferring functional proteins and RNAs between cells. Here, to clarify the function of exosomes during influenza virus infection, we characterized lung-derived exosomal microRNAs (miRNAs). Among the detected miRNAs, miR-483-3p was present at high levels in bronchoalveolar lavage fluid (BALF) exosomes during infection of mice with various strains of influenza virus, and miR-483-3p transfection potentiated gene expression of type I interferon and proinflammatory cytokine upon viral infection of MLE-12 cells. RNF5, a regulator of the RIG-I signaling pathway, was identified as a target gene of miR-483-3p. Moreover, we found that CD81, another miR-483-3p target, functions as a negative regulator of RIG-I signaling in MLE-12 cells. Taken together, this study indicates that BALF exosomal miRNAs may mediate the antiviral and inflammatory response to influenza virus infection. [ABSTRACT FROM AUTHOR]

Influenza A and B viruses have eight-segmented, single-stranded, negativesense RNA genomes, whereas influenza C and D viruses have seven-segmented genomes. Each genomic RNA segment exists in the form of a ribonucleoprotein complex (RNP) in association with nucleoproteins and an RNA-dependent RNA polymerase in virions. Influenza D virus was recently isolated from swine and cattle, but its morphology is not fully studied. Here, we examined the morphological characteristics of D/bovine/Yamagata/10710/2016 (D/Yamagata) and C/Ann Arbor/50 (C/AA), focusing on RNPs packaged within the virions. By scanning transmission electron microscopic tomography, we found that more than 70% of D/Yamagata and C/AA virions packaged eight RNPs arranged in the "1+7" pattern as observed in influenza A and B viruses, even though type C and D virus genomes are segmented into only seven segments. These results imply that influenza viruses generally package eight RNPs arranged in the "1+7" pattern regardless of the number of RNA segments in their genome. [ABSTRACT FROM AUTHOR]

Ferrets and mice are frequently used as animal models for influenza research. However, ferrets are demanding in terms of housing space and handling, whereas mice are not naturally susceptible to infection with human influenza A or B viruses. Therefore, prior adaptation of human viruses is required for their use in mice. In addition, there are no mouse-adapted variants of the recent H3N2 viruses, because these viruses do not replicate well in mice. In this study, we investigated the susceptibility of Syrian hamsters to influenza viruses with a view to using the hamster model as an alternative to the mouse model. We found that hamsters are sensitive to influenza viruses, including the recent H3N2 viruses, without adaptation. Although the hamsters did not show weight loss or clinical signs of H3N2 virus infection, we observed pathogenic effects in the respiratory tracts of the infected animals. All of the H3N2 viruses tested replicated in the respiratory organs of the hamsters, and some of them were detected in the nasal washes of infected animals. Moreover, a 2009 pandemic (pdm09) virus and a seasonal H1N1 virus, as well as one of the two H3N2 viruses, but not a type B virus, were transmissible by the airborne route in these hamsters. Hamsters thus have the potential to be a small-animal model for the study of influenza virus infection, including studies of the pathogenicity of H3N2 viruses and other strains, as well as for use in H1N1 virus transmission studies. [ABSTRACT FROM AUTHOR]

Hepatitis B virus (HBV) is a virus whose replication cycle cannot be completely reproduced using cultured cell lines. Here, we report an engineered cell line capable of supporting the complete HBV life cycle. We generated HepG2 cells over-expressing the HBV entry receptor human NTCP (sodium taurocholate cotransporting polypeptide), and defective in RIG-I (retinoic acid-inducible gene-I)-like receptor signaling, by knocking down the IPS-1 (IFNß-promoter stimulator-1) adaptor molecule. The resultant NtG20.i7 cells were susceptible to HBV, and its replication was detectable at 14 days postinfection and persisted for at least 35 days with a gradual increase of HBV core expression. The cells produced infectious HBV in the culture supernatant, and the addition of preS1 peptide myr47-WT, which blocks HBV entry, impaired the persistence of the infection. These findings suggest that the persistence of the infection was maintained by continuous release of infectious HBV virions and their re-infection. This system is useful for expanding our basic understanding of the HBV replication cycle and for screening of anti-HBV chemicals. [ABSTRACT FROM AUTHOR]

Autophagy is an intracellular degradation pathway conserved in eukaryotes. Among core autophagy-related (Atg) proteins, mammalian Atg9A is the sole multi-spanning transmembrane protein, and both of its N- and C-terminal domains are exposed to the cytoplasm. It is known that Atg9A travels through the trans-Golgi network (TGN) and the endosomal system under nutrient-rich conditions, and transiently localizes to the autophagosome upon autophagy induction. However, the significance of Atg9A trafficking for autophagosome formation remains elusive. Here, we identified sorting motifs in the N-terminal cytosolic stretch of Atg9A that interact with the adaptor protein AP-2. Atg9A with mutations in the sorting motifs could not execute autophagy and was abnormally accumulated at the recycling endosomes. The combination of defects in autophagy and Atg9A accumulation in the recycling endosomes was also found upon the knockdown of TRAPPC8, a specific subunit of the TRAPPIII complex. These results show directly that the trafficking of Atg9A through the recycling endosomes is an essential step for autophagosome formation. [ABSTRACT FROM AUTHOR]

We have successfully grown high quality InxGa1-xAs metamorphic layer on GaAs (111)A using molecular beam epitaxy. Inserting a thin 3.0-7.1 monolayer (ML) InAs interlayer between the In0.25Ga0.75As and GaAs allowed the formation of a nearly lattice-relaxed In0.25Ga0.75As with a very flat upper surface. However, when the thickness of the inserted InAs is thinner or thicker than these values, we observed degradation of crystal quality and/or surface morphology. We also revealed this technique to be applicable to the formation of a high quality metamorphic InxGa1-xAs layer with a range of In compositions (0.25 ≤ x ≤ 0.78) on GaAs (111)A. Cross-sectional scanning transmission electron microscope studies revealed that misfit dislocations formed only at the interface of InAs and GaAs, not at the interface of In0.25Ga0.75As and InAs. From the dislocation density analysis, it is suggested that the dislocation density was decreased by growing In0.25Ga0.75As on InAs, which effectively contribute the strain relaxation of In0.25Ga0.75As. The InGaAs/InAlAs quantum wells that were formed on the metamorphic layers exhibit clear photoluminescence emissions up to room temperature. [ABSTRACT FROM AUTHOR]

The PA, PB1, and PB2 subunits, components of the RNA-dependent RNA polymerase of influenza A virus, are essential for viral transcription and replication. The PB2 subunit binds to the host RNA cap (7-methylguanosine triphosphate (m7GTP)) and supports the endonuclease activity of PA to "snatch" the cap from host pre-mRNAs. However, the structure of PB2 is not fully understood, and the functional sites remain unknown. In this study, we describe a novel Val/Arg/Gly (VRG) site in the PB2 cap-binding domain, which is involved in interaction with acetyl-CoA found in eukaryotic histone acetyltransferases (HATs). In vitro experiments revealed that the recombinant PB2 cap-binding domain that includes the VRG site interacts with acetyl-CoA; moreover, it was found that this interaction could be blocked by CoA and various HAT inhibitors. Interestingly, m7GTP also inhibited this interaction, suggesting that the same active pocket is capable of interacting with acetyl-CoA and m7GTP. To elucidate the importance of the VRG site on PB2 function and viral replication, we constructed a PB2 recombinant protein and recombinant viruses including several patterns of amino acid mutations in the VRG site. Substitutions of the valine and arginine residues or of all 3 residues of the VRG site to alanine significantly reduced the binding ability of PB2 to acetyl-CoA and its RNA polymerase activity. Recombinant viruses containing the same mutations could not be replicated in cultured cells. These results indicate that the PB2VRG sequence is a functional site that is essential for acetyl-CoA interaction, RNA polymerase activity, and viral replication. [ABSTRACT FROM AUTHOR]

Herpesviruses have evolved a unique mechanism for nuclear egress of nascent progeny nucleocapsids: the nucleocapsids bud through the inner nuclear membrane into the perinuclear space between the inner and outer nuclear membranes (primary envelopment), and enveloped nucleocapsids then fuse with the outer nuclear membrane to release nucleocapsids into the cytoplasm (de-envelopment). We have shown that the herpes simplex virus 1 (HSV-1) major virion structural protein UL47 (or VP13/VP14) is a novel regulator for HSV-1 nuclear egress. In particular, we demonstrated the following: (i) UL47 formed a complex(es) with HSV-1 proteins UL34, UL31, and/or Us3, which have all been reported to be critical for viral nuclear egress, and these viral proteins colocalized at the nuclear membrane in HSV-1-infected cells; (ii) the UL47-nullmutation considerably reduced primary enveloped virions in the perinuclear space although capsids accumulated in the nucleus; and (iii) UL47 was detected in primary enveloped virions in the perinuclear space by immunoelectron microscopy. These results suggested that UL47 promoted HSV-1 primary envelopment, probably by interacting with the critical HSV-1 regulators for viral nuclear egress and by modulating their functions. [ABSTRACT FROM AUTHOR]

We demonstrate the formation of InAs quantum dots (QDs) on InAlAs/InP(111)A by means of droplet epitaxy. The C3μ symmetry of the (111)A substrate enabled us to realize highly symmetric QDs that are free from lateral elongations. The QDs exhibit a disk-like truncated shape with an atomically flat top surface. Photoluminescence signals show broad-band spectra at telecommunication wavelengths of 1.3 and 1.5 μm. Strong luminescence signals are retained up to room temperature. Thus, our QDs are potentially useful for realizing an entangled photon-pair source that is compatible with current telecommunication fiber networks. [ABSTRACT FROM AUTHOR]

Autophagy is a bulk protein-degradation process that is regulated by many factors. In this study, we quantitatively assessed the contribution of each essential yeast gene to autophagy. Of the contributing factors that we identified, we focused on the TRAPPIII complex, which was recently shown to act as a guanine-nucleotide exchange factor for the Rab small GTPase Ypt1. Autophagy is defective in the TRAPPIII mutant under nutrient-rich conditions (Cvt pathway), but starvation-induced autophagy is only partially affected. Here, we show that TRAPPIII functions at the Golgi complex to receive general retrograde vesicle traffic from early endosomes. Cargo proteins in this TRAPPIII-dependent pathway include Atg9, a transmembrane protein that is essential for autophagy, and Snc1, a SNARE unrelated to autophagy. When cells were starved, further disruption of vesicle movement from late endosomes to the Golgi caused defects in Atg9 trafficking and autophagy. Thus, TRAPPIII-dependent sorting pathways provide Atg9 reservoirs for pre-autophagosomal structure and phagophore assembly sites under nutrient-rich conditions, whereas the late endosome-to-Golgi pathway is added to these reservoirs when nutrients are limited. This clarification of the role of TRAPPIII elucidates how general membrane traffic contributes to autophagy. [ABSTRACT FROM AUTHOR]

Although ubiquitin is thought to be important for the autophagic sequestration of invading bacteria (also called xenophagy), its precise role remains largely enigmatic. Here we determined how ubiquitin is involved in this process. After invasion, ubiquitin is conjugated to host cellular proteins in endosomes that contain Salmonella or transfection reagent-coated latex (polystyrene) beads, which mimic invading bacteria. Ubiquitin is recognized by the autophagic machinery independently of the LC3-ubiquitin interaction through adaptor proteins, including a direct interaction between ubiquitin and Atg16L1. To ensure that invading pathogens are captured and degraded, Atg16L1 targeting is secured by two backup systems that anchor Atg16L1 to ubiquitin-decorated endosomes. Thus, we reveal that ubiquitin is a pivotal molecule that connects bacteria-containing endosomes with the autophagic machinery upstream of LC3. [ABSTRACT FROM AUTHOR]

Ebola virus (EBOV) protein L (EBOL) acts as a viral RNA-dependent RNA polymerase. To better understand the mechanisms underlying the transcription and replication of the EBOV genome, we sought to identify cellular factors involved in these processes via their coimmunoprecipitation with EBOL and by mass spectrometry. Of 65 candidate proteins identified, we focused on DNA topoisomerase 1 (TOP1), which localizes to the nucleus and unwinds helical DNA. We found that in the presence of EBOL, TOP1 colocalizes and interacts with EBOL in the cytoplasm, where transcription and replication of the EBOV genome occur. Knockdown of TOP1 markedly reduced virus replication and viral polymerase activity. We also found that the phosphodiester bridge-cleaving and recombination activities of TOP1 are required for the polymerase activity of EBOL. These results demonstrate that TOP1 is an important cellular factor for the transcription and replication of the EBOV genome and, as such, plays a key role in the EBOV life cycle. [ABSTRACT FROM AUTHOR]

Using photoluminescence microscopy enhanced by magnetic resonance, we visualize in real space both electron and nuclear polarization occurring in nonequilibrium fraction quantum Hall (FQH) liquids. We observe stripelike domain regions comprising FQH excited states which discretely form when the FQH liquid is excited by a source-drain current. These regions are deformable and give rise to bidirectionally polarized nuclear spins as spin-resolved electrons flow across their boundaries. [ABSTRACT FROM AUTHOR]

We perform real-space imaging of propagating magnetic domains in the fractional quantum Hall system using spin-sensitive photoluminescence microscopy. The propagation is continuous and proceeds in the direction of the conventional current, i.e., opposite to the electron flow direction. The mechanism of motion is shown to be connected to polarized nuclear spins around the domain walls. The propagation velocity increases when nuclei are depolarized, and decreases when the source-drain current generating this nuclear polarization is increased. We discuss how these phenomena may arise from spin interactions along the domain walls. [ABSTRACT FROM AUTHOR]