Structural Studies of NediV-IRES-Mediated Translation Initiation

Viruses require a host cell to replicate and proliferate; upon infection they appropriate host resources and molecular machines. Specifically, viruses use ribosomes of the host to translate the information in their genome. Some viruses with single-stranded RNA genomes contain highly structured non-coding regions of RNA called internal ribosome entry sites (IRESs) which are used to hijack the host’s ribosomes through a non-canonical cap-independent initiation pathway. Canonical translation initiation is a highly complex and regulated process: at least a dozen translation factors are necessary, and it is the rate-limiting step in eukaryotic translation. Viruses containing an IRES forgo canonical eukaryotic translation initiation factors and bypass some steps of canonical translation initiation by mimicking part of the host’s initiation machinery. The simplest among these IRESs are found in the intergenic region (IGR) of viruses in the family Dicistroviridae. These type IV IRESs from dicistroviruses have been structurally characterized in great detail in using the cricket paralysis virus (CrPV) and Israeli Acute Paralysis Virus (IAPV). To better understand how structure affects the function of these type IV IRESs, using single-particle cryo-electron microscopy (cryo-EM), we have characterized a recently discovered IRES found in the IGR of the genome of Nedicistrovirus (NediV). Four complexes that represent each step in the alternative translation initiation mechanism were prepared and analyzed to solve the 3D structure and characterize the mechanism by which the NediV-IRES captures host ribosomes. With this, we were able to understand how the shorter stem-loop V (SL-V) of NediV-IRES impacts the well-characterized interaction of SL-V with eukaryotic small subunit ribosomal protein 25 (eS25) (Landry et al., 2009), which is important for the IRES:40S complex formation. This shortened stem-loop has been shown to fold in a way that does not support stable binding to the small ribosomal subunit (40S) and subsequent recruitment of the large ribosomal subunit (60S). NediV-IRES, rather, relies on direct recruitment of the 80S ribosome, which has been seen more commonly at low concentrations of Mg²⁺ for CrPV-IRES (Petrov et al., 2016). Solved structures also suggest that upon loading, NediV-IRES skips the first eEF2-dependent pseudo-translocation step necessary to bind to the ribosomal P site without the need of eEF2. Because of their simplicity, these type IV IRESs represent a robust potential tool for cell-free and vector-driven translation. Due to these structural and mechanistic differences observed, we propose that NediV-IRES, along with the NediV-like Antarctic picorna-like virus 1 (APLV-1)-IRES (Lu, 2019), represents a novel type IV IRES subclass.

Applying medicinal chemistry strategies to understand odorant discrimination

Associating an odorant’s chemical structure with its percept is a long-standing challenge. One hindrance may come from the adoption of the organic chemistry scheme of molecular description and classification. Chemists classify molecules according to characteristics that are useful in synthesis or isolation, but which may be of little importance to a biological sensory system. Accordingly, we look to medicinal chemistry, which emphasizes biological function over chemical form, in an attempt to discern which among the many molecular features are most important for odour discrimination. Here we use medicinal chemistry concepts to assemble a panel of molecules to test how heteroaromatic ring substitution of the benzene ring will change the odour percept of acetophenone. This work allows us to describe an extensive rule in odorant detection by mammalian olfactory receptors. Whereas organic chemistry would have predicted the ring size and composition to be key features, our work reveals that the topological polar surface area is the key feature for the discrimination of these odorants

Global disparities in surgeons’ workloads, academic engagement and rest periods: the on-calL shIft fOr geNEral SurgeonS (LIONESS) study

: The workload of general surgeons is multifaceted, encompassing not only surgical procedures but also a myriad of other responsibilities. From April to May 2023, we conducted a CHERRIES-compliant internet-based survey analyzing clinical practice, academic engagement, and post-on-call rest. The questionnaire featured six sections with 35 questions. Statistical analysis used Chi-square tests, ANOVA, and logistic regression (SPSS® v. 28). The survey received a total of 1.046 responses (65.4%). Over 78.0% of responders came from Europe, 65.1% came from a general surgery unit; 92.8% of European and 87.5% of North American respondents were involved in research, compared to 71.7% in Africa. Europe led in publishing research studies (6.6 ± 8.6 yearly). Teaching involvement was high in North America (100%) and Africa (91.7%). Surgeons reported an average of 6.7 ± 4.9 on-call shifts per month, with European and North American surgeons experiencing 6.5 ± 4.9 and 7.8 ± 4.1 on-calls monthly, respectively. African surgeons had the highest on-call frequency (8.7 ± 6.1). Post-on-call, only 35.1% of respondents received a day off. Europeans were most likely (40%) to have a day off, while African surgeons were least likely (6.7%). On the adjusted multivariable analysis HDI (Human Development Index) (aOR 1.993) hospital capacity > 400 beds (aOR 2.423), working in a specialty surgery unit (aOR 2.087), and making the on-call in-house (aOR 5.446), significantly predicted the likelihood of having a day off after an on-call shift. Our study revealed critical insights into the disparities in workload, access to research, and professional opportunities for surgeons across different continents, underscored by the HDI