In-plane superfluid density and microwave conductivity of the organic superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br: evidence for d-wave pairing and resilient quasiparticles

We report the in-plane microwave surface impedance of a high-quality single crystal of kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br. In the superconducting state, we find three independent signatures of d-wave pairing: (i) a strong, linear temperature dependence of superfluid density; (ii) deep in the superconducting state the quasiparticle scattering rate Gamma similar to T-3; and (iii) no BCS coherence peak is observed in the quasiparticle conductivity. Above T-c, the Kadowaki-Woods ratio and the temperature dependence of the in-plane conductivity show that the normal state is a Fermi liquid below similar or equal to 23 K, yet resilient quasiparticles dominate the transport up to similar or equal to 50 K

Prevalence and risk factors for Betaherpesvirus DNAemia in children >3 weeks and <2 years of age admitted to a large referral hospital in sub-Saharan Africa

Background. Betaherpesviruses are established causes of morbidity and mortality in immunosuppressed patient groups but have been little studied in sub-Saharan Africa, the epicenter of the human immunodeficiency virus (HIV) pandemic. In this region, primary infections with human cytomegalovirus (HCMV) and human herpesvirus type 6 (HHV-6) type 6 are endemic in infancy, but the clinical impact of these infections among pediatric inpatient groups is poorly characterized and assumptive, based largely on data from Western populations. Methods. We used TaqMan polymerase chain reaction to screen sera from a group of 303 pediatric inpatients aged between 3 weeks and 2 years, at the University Teaching Hospital in Lusaka, Zambia. We report the prevalence of DNAemia and viral loads within this patient group, and evaluate possible clinical associations/risk factors for betaherpesvirus infections in these hospitalized children. Results. We detected betaherpesvirus DNAemia in 59.1% (179/303) of children. HCMV was the most prevalent (41.3%), followed by HHV-6B (20.5%), HHV-7 (20.1%), and HHV-6A (0.3%). HIV infection (odds ratio OR], 2.31; 95% confidence interval CI], 1.37-3.90; P = .002), being underweight (OR, 1.82; 95% CI, 1.06-3.12; P = .03), and an admission diagnosis of suspected meningitis (OR, 5.72; 95% CI, 1.07-30.5; P = .041) were independently associated with an increased odds of HCMV DNAemia. Conversely, HHV-6B and HHV-7 DNAemia were not associated with HIV, underweight, or admission diagnosis. Median HCMV viral load was moderately but significantly higher in HIV-infected children. Conclusions. Highly prevalent HCMV DNAemia was independently associated with HIV infection and being underweight across all age groups, and was also associated with meningitis, with previously underappreciated implications for the health and development of African children

The C-terminal domain of eukaryotic initiation factor 5 promotes start codon recognition by its dynamic interplay with eIF1 and eIF2 beta

Recognition of the proper start codon on mRNAs is essential for protein synthesis, which requires scanning and involves eukaryotic initiation factors (eIFs) eIF1, eIF1A, eIF2, and eIF5. The carboxyl terminal domain (CTD) of eIF5 stimulates 43S preinitiation complex (PIC) assembly; however, its precise role in scanning and start codon selection has remained unknown. Using nuclear magnetic resonance (NMR) spectroscopy, we identified the binding sites of eIF1 and eIF2β on eIF5-CTD and found that they partially overlapped. Mutating select eIF5 residues in the common interface specifically disrupts interaction with both factors. Genetic and biochemical evidence indicates that these eIF5-CTD mutations impair start codon recognition and impede eIF1 release from the PIC by abrogating eIF5-CTD binding to eIF2β. This study provides mechanistic insight into the role of eIF5-CTD's dynamic interplay with eIF1 and eIF2β in switching PICs from an open to a closed state at start codons.publishedVersio

Human cytomegalovirus infection of langerhans-type dendritic cells does not require the presence of the gH/gL/UL128-131A complex and is blocked after nuclear deposition of viral genomes in immature cells

Human cytomegalovirus (CMV) enters its host via the oral and genital mucosae. Langerhans-type dendritic cells (LC) are the most abundant innate immune cells at these sites, where they constitute a first line of defense against a variety of pathogens. We previously showed that immature LC (iLC) are remarkably resistant to CMV infection, while mature LC (mLC) are more permissive, particularly when exposed to clinical-strain-like strains of CMV, which display a pentameric complex consisting of the viral glycoproteins gH, gL, UL128, UL130, and UL131A on their envelope. This complex was recently shown to be required for the infection of immature monocyte-derived dendritic cells. We thus sought to establish if the presence of this complex is also necessary for virion penetration of LC and if defects in entry might be the source of iLC resistance to CMV. Here we report that the efficiency of LC infection is reduced, but not completely abolished, in the absence of the pentameric complex. While virion penetration and nuclear deposition of viral genomes are not impaired in iLC, the transcription of the viral immediate early genes UL122 and UL123 and of the delayed early gene UL50 is substantially lower than that in mLC. Together, these data show that the UL128, UL130, and UL131A proteins are dispensable for CMV entry into LC and that progression of the viral cycle in iLC is restricted at the step of viral gene expression

Viral Mimicry of Cdc2/Cyclin-Dependent Kinase 1 Mediates Disruption of Nuclear Lamina during Human Cytomegalovirus Nuclear Egress

The nuclear lamina is a major obstacle encountered by herpesvirus nucleocapsids in their passage from the nucleus to the cytoplasm (nuclear egress). We found that the human cytomegalovirus (HCMV)-encoded protein kinase UL97, which is required for efficient nuclear egress, phosphorylates the nuclear lamina component lamin A/C in vitro on sites targeted by Cdc2/cyclin-dependent kinase 1, the enzyme that is responsible for breaking down the nuclear lamina during mitosis. Quantitative mass spectrometry analyses, comparing lamin A/C isolated from cells infected with viruses either expressing or lacking UL97 activity, revealed UL97-dependent phosphorylation of lamin A/C on the serine at residue 22 (Ser22). Transient treatment of HCMV-infected cells with maribavir, an inhibitor of UL97 kinase activity, reduced lamin A/C phosphorylation by approximately 50%, consistent with UL97 directly phosphorylating lamin A/C during HCMV replication. Phosphorylation of lamin A/C during viral replication was accompanied by changes in the shape of the nucleus, as well as thinning, invaginations, and discrete breaks in the nuclear lamina, all of which required UL97 activity. As Ser22 is a phosphorylation site of particularly strong relevance for lamin A/C disassembly, our data support a model wherein viral mimicry of a mitotic host cell kinase activity promotes nuclear egress while accommodating viral arrest of the cell cycle