Biology subjects

Moshiri, H.

Publications and source records attributed to Moshiri, H..

3 recordsLinked to original sources

bioRxiv2019

Binding to the Ribosome by Eukaryotic Initiation Factor 4B Drives Yeast Translational Control in Response to Urea

The yeast eukaryotic initiation factor 4B binds the 40S subunit in translation preinitiation complexes (PICs), promoting mRNA binding. Recent evidence suggests mRNAs have variable dependence on eIF4B, suggesting this factor could promote changes in mRNA selection for translation, in order to adapt to stressors. However, the importance of eIF4B and its constituent domains for mRNA selection under diverse cellular and environmental conditions remain undefined. Here we compared the effects of disrupting eIF4B RNA- and ribosome-binding motifs under ~1400 growth conditions. The RNA-Recognition Motif (RRM) was dispensable for stress responses, but the 40S-binding N-terminal Domain (NTD) promoted growth in response to various stressors. In particular, the NTD conferred a strong growth advantage in the presence of urea. Ribosome profiling revealed that the NTD promoted translation of mRNAs with long and highly structured 5-prime untranslated regions, both with and without urea exposure. Our results suggest eIF4B controls mRNA loading and scanning as a part of the PIC, rather than by activating mRNPs prior to ribosome binding. Furthermore, our data indicate the yeast response to urea includes a translational component, driven by production of proteins associated with the cellular periphery. Together our analyses suggest general eIFs can promote diverse cellular responses.

molecular biology↗

bioRxiv2019

The Marginal Cells of the Caenorhabditis elegans Pharynx Scavenge Cholesterol and Other Hydrophobic Small Molecules

The nematode worm Caenorhabditis elegans is a bacterivore filter feeder. Through the contraction of the worms pharynx, a bacterial suspension is sucked into the pharynxs lumen. Excess liquid is then shunted out of the buccal cavity through ancillary channels that are made from specialized pharyngeal cells called marginal cells. Through the characterization of our library of worm-bioactive small molecules (a.k.a. wactives), we found that more than one third of wactives visibly accumulate inside of the marginal cells as crystals or globular spheres. Wactives that visibly accumulate are typically more hydrophobic than those that do not. To understand why wactives accumulate specifically in marginal cells, we performed a forward genetic screen for mutants that resist the lethality associated with one crystallizing wactive. We identified a presumptive sphingomyelin-synthesis pathway that is necessary for crystal and sphere accumulation. Sphingomyelin is a phospholipid that is enriched in the outer leaflet of the plasma membranes of most metazoans. We find that the predicted terminal enzyme of this pathway, sphingomyelin synthase 5 (SMS-5), is expressed in the pharynx, contributes to sphingomyelin abundance, and that its expression in marginal cells is sufficient for wactive accumulation. We also find that the expression of SMS-5 in the marginal cells is necessary for the proper absorption of exogenous cholesterol, without which C. elegans cannot develop. We conclude that the sphingomyelin-rich plasma membrane of the marginal cells acts as a sink to scavenge important hydrophobic nutrients from the filtered liquid that might otherwise be shunted back into the environment. One sentence summaryThe anterior pharynx of C. elegans is a Sink for Hydrophobic Small Molecules

developmental biology↗

bioRxiv2017

Humpback whales of the Persian Gulf

The humpback whale has long been considered a rare straggler into the Persian Gulf, however new evidence contradicts this concept. We here critically review published and new records for Megaptera novaeangliae occurrence in the Gulf for the period 1883-2017. Of eight authenticated records (6 specimens, 2 live-sightings), seven are contemporary cases while one is a mid-Holocene specimen from UAE. An additional four are possible but unsubstantiated reports. Four regional, current, range states are confirmed, i.e. Iran, Iraq, Kuwait and Qatar. Four of the five newly reported cases are from Irans coastal waters. We conclude that the Persian Gulf is part of the habitual range of the Arabian Sea humpback whale population, and has been since at least the mid-Holocene. It is unknown whether frequent passage occurs through the Strait of Hormuz or whether whales are (semi)resident. The low abundance of this endangered population and frequent deleterious anthropogenic events, particularly ship strikes and net entanglements, are cause for major concern. In view of its historical and taxonomic relevance, the formal description of Megaptera indica Gervais, 1883, from Iraq, now thought to be a subspecies M. novaeangliae indica, is here translated from French.

zoology↗