Stable m7G Cap-Distal 5'UTR Hairpin Structure Mediates Distinct 40S and 60S Binding Dynamics

The 5' untranslated region (UTR) of diverse mRNAs contains secondary structures that can influence protein synthesis by modulating the initiation step of translation. Studies support the ability of these structures to inhibit 40S subunit recruitment and scanning, but the dynamics of ribosomal subunit interactions with mRNA remain poorly understood. Here, we developed a reconstituted Saccharomyces cerevisiae cell-free translation system with fluorescently labeled ribosomal subunits. We applied this extract and single-molecule fluorescence microscopy to monitor, in real time, individual 40S and 60S interactions with mRNAs containing 5' UTR hairpin structures with varying thermostability. In comparison to mRNAs containing no or weak 5' UTR hairpins (ΔG >= -5.4 kcal/mol), mRNAs with stable hairpins (ΔG <= -16.5 kcal/mol) showed reduced numbers of 60S recruitment to mRNA, consistent with the expectation of reduced translation efficiency for such mRNAs. Interestingly, such mRNAs showed increased numbers of 40S recruitment events to individual mRNAs but with shortened duration on mRNA. Correlation analysis showed that these unstable 40S binding events were nonproductive for 60S recruitment. Furthermore, although the mRNA sequence is long enough to accommodate multiple 40S, individual mRNAs are predominantly observed to engage with a single 40S at a time, indicating the sequestering of mRNA 5' end by initiating 40S. Altogether, these observations suggest that stable cap-distal hairpins in 5' UTR reduce initiation and translation efficiency by destabilizing 40S-mRNA interactions and promoting 40S dissociation from mRNA. The premature 40S dissociation frees mRNA 5'-end accessibility for new initiation events, but the increased rate of 40S recruitment is insufficient to compensate for the reduction of initiation efficiency due to premature 40S dissociation. This study provides the first single-molecule kinetic characterization of 40S/60S interactions with mRNA during cap-dependent initiation and the modulation of such interactions by cap-distal 5' UTR hairpin structures.

A Comparative Study of Implications of the Term of History in the Islamic and Western Perception

The present study deals with the term of history linguistically and terminologically from Arab and Western Europe. This term is radically intertwined between East and West, specifically the Greek language. The present study covers the views of ancient historians and modernists as much as possible to have a clear idea of the topic. Section two is devoted to answering the important question of whether history is a science or an art by presenting most of the opinions that have been put forward in this regard, whether by Western or Arab historians to ultimately reach a comprehensive, complete, and final answer, at least until present time. Section three is related to the science of history for Muslims and its impact on the science of history in the West. Rosenthal’s opinion, which reflects the views of the majority of orientalists will be explained to respond to it showing evidence of the extent of this influence and how it was the initiation step and the most influential catalyst for the intellectual renaissance of Europe in general and in historical writing in particular.

852. Bridging the Gap in PrEP Provider Training: An Implementation Science Study

Background Training healthcare providers in a variety of clinical settings to deliver pre-exposure prophylaxis (PrEP) is a key component of the Ending the HIV Epidemic (EHE) initiative. Self-efficacy, the individual’s belief in their ability to carry out the steps of PrEP delivery, is a core part of provider training and necessary for successful PrEP implementation. We characterized self-efficacy among providers from family planning (FP) clinics that do not provide PrEP to inform provider training strategies. Methods We surveyed providers (any clinical staff who could screen, counsel, or prescribe PrEP) from FP clinics in 18 Southern states (Feb-June 2018, N=325 respondents from 224 clinics not providing PrEP) using contraception- and PrEP-specific self-efficacy questions (overall and grouped into PrEP delivery steps: screening, initiation, and follow-up). We compared self-efficacy scores (5-point Likert scale) by prescriber status, between PrEP delivery steps, and used linear mixed models to analyze provider-, clinic-, and county-level covariates associated with overall PrEP self-efficacy. Results Among 325 FP providers, self-efficacy scores were lowest in the PrEP initiation step, higher in follow-up, and highest in screening (p &lt; 0.0001, Table). Mean overall PrEP self-efficacy scores were significantly higher among prescribers compared to non-prescribers (p &lt; 0.0001). However, providers reported lowest self-efficacy regarding insurance navigation for PrEP with no significant difference by prescriber status. The mixed model demonstrated overall PrEP self-efficacy was positively associated with favorable PrEP attitudes among non-prescribers, PrEP knowledge among prescribers, and contraception self-efficacy in both groups, but was not associated with availability of insurance navigation on-site or other covariates (Figure). Provider Self-Efficacy along the PrEP Delivery Model stratified by prescriber status Conclusion FP providers reported low confidence in their ability to perform the steps that comprise PrEP initiation. Provider training focused on elements of PrEP initiation are critical to improve PrEP implementation and EHE initiatives. Alternatively, programs employing referral or telehealth models to support the PrEP initiation step can successfully bridge this gap. Disclosures All Authors: No reported disclosures

In Situ Generation of Radical Initiators: Air Stable Amine-Borane Complexes Promote Atom Transfer Radical Additions of Alkyl Halides to Alkenes

Despite their instability, carbon-centered radicals have been involved as intermediates in many organic transformations that are essential to mankind. Radical polymerization,1-5 for example, provides a large part of polyacrylates and polystyrenes used as commodities in our everyday life. On a molecular level, the outcome of radical-mediated reactions is usually very different from those obtained via classical ionic based organic reactions. This is known since the 1930’s6 and has witnessed extensive developments such as radical cyclization or Atom Transfer Radical Additions (ATRA)7-9 . Radical processes10 typically begin with an initiation step in which the first radical species is created. It is eventually followed by one or several transfer steps which ultimately conduct to the formation of the main radical intermediate responsible for the reaction. The propagation steps of the radical chain are a succession of radical based transformations which, combined, outline the expected transformation.

In Situ Generation of Radical Initiators: Air Stable Amine-Borane Complexes Promote Atom Transfer Radical Additions of Alkyl Halides to Alkenes

Despite their instability, carbon-centered radicals have been involved as intermediates in many organic transformations that are essential to mankind. Radical polymerization,1-5 for example, provides a large part of polyacrylates and polystyrenes used as commodities in our everyday life. On a molecular level, the outcome of radical-mediated reactions is usually very different from those obtained via classical ionic based organic reactions. This is known since the 1930’s6 and has witnessed extensive developments such as radical cyclization or Atom Transfer Radical Additions (ATRA)7-9 . Radical processes10 typically begin with an initiation step in which the first radical species is created. It is eventually followed by one or several transfer steps which ultimately conduct to the formation of the main radical intermediate responsible for the reaction. The propagation steps of the radical chain are a succession of radical based transformations which, combined, outline the expected transformation.

"BIO-BASED EPOXY RESINS AND COMPOSITES FROM EPOXIDIZED LINSEED OIL CROSSLINKED WITH DIFFERENT CYCLIC ANHYDRIDES AND THEIR COMBINATION WITH LIGNIN"

Biobased resins and composites with high biobased carbon content were prepared and characterized. Epoxidized linseed oil (ELO) was copolymerized with four cyclic anhydrides, the initiation step being optimized in terms of initiator nature and its ratio. The optimized ELO/anhydride formulations were combined with a high load of lignin, as biofiller, ~30 wt%. The obtained materials were characterized by TGA, DSC, DMA, gel content, water absorption (WA) and Shore hardness tests. The results revealed very good thermomechanical properties, high gel content and low WA, opening the way to their utilization as a sustainable alternative to oil-based resins and composites.

Trajectories of Cotton Fiber Initiation: A Regulatory Perspective

The epidermal cells on the surface of the cotton ovules undergo differentiation to produce fibers, which are single-celled hair-like protrusions resembling the plant trichomes. The initiation of these unicellular fibers from the cotton ovule surface is a complex and tightly regulated process. The initiation step is the cell fate-determining stage, which leads to the commitment of cells that eventually developed into fibers, thus becomes the most crucial phase in fiber development. The in-depth knowledge of molecular regulation is a prerequisite to get a clear view of the fiber initiation process's genetic and epigenetic control. The identification and functional validation of cotton fiber initiation-related genes, few fibreless mutants, transcription factors, microRNAs, epigenetic regulators, as well as the elucidation of the role of phytohormones as signaling molecules, has played a significant role in understanding the cotton fiber initiation process at the molecular level. This review focuses on the comprehensive information regarding the genetic and epigenetic regulation of cotton fiber initiation. Thus, the review will provide readers insight into mechanistic details that operate during cotton fiber initiation.

Extensive 5’-Surveillance Guards Against Non-Canonical NAD-Caps of Nuclear mRNAs in Yeast

SummaryThe ubiquitous redox coenzyme nicotinamide adenine dinucleotide (NAD) acts as a non-canonical cap structure on prokaryotic and eukaryotic ribonucleic acids. Here we find that in budding yeast, NAD-RNAs are abundant (>1400 species), short (<170 nt), and mostly correspond to mRNA 5’-ends. The modification percentage is low (<5%). NAD is incorporated during the initiation step by RNA polymerase II, which uses distinct promoters with a YAAG core motif for this purpose. Most NAD-RNAs are 3’-truncated. At least three decapping enzymes, Rai1, Dxo1, and Npy1, guard against NAD-RNA at different cellular locations, targeting overlapping transcript populations. NAD-mRNAs do not support translation in vitro. Our work indicates that in budding yeast, most of the NAD incorporation into RNA seems to be accidental and undesirable to the cell, which has evolved a diverse surveillance machinery to prematurely terminate, decap and reject NAD-RNAs.In BriefIn budding yeast, most of the NAD incorporation into RNA seems to be accidental and undesirable to the cell, which has evolved a diverse surveillance machinery to prematurely terminate, decap and reject NAD-RNAs.Graphical AbstractHighlightsYeast cells have thousands of short NAD-RNAs related to the 5’-ends of mRNAsRNA polymerase II prefers a YAAG promoter motif for NAD incorporation into RNANAD-RNA is strongly guarded against by Rai1, Dxo1, and Npy1 decapping enzymes at different subcellular sitesIn vitro, NAD-mRNAs are rejected from translation

Self-Metathesis of Methyl Oleate Using Ru-NHC Complexes: A Kinetic Study

A kinetic study concerning the self-metathesis of methyl oleate and methyl elaidate was performed, using a variety of NHC-ruthenium pre-catalysts, bearing either mesityl groups or di-isopropyl-phenyl groups on the NHC ligand and various trans ligands with respect to the NHC unit. We showed that the system can be satisfactorily described using one initiation constant per pre-catalyst and four propagation constants that, conversely, do not depend on the pre-catalyst. The difference of reactivity with oleate (Z) and elaidate (E) can be fully explained by the propagation parameters; the studied pre-catalysts initiate with the same rate starting from the Z or the E olefin. The ranking of the propagation parameters is driven by the thermodynamic equilibrium. The transformation rates of Z and E isomers is only driven by these propagation constants and nothing differentiates the initiation step.