The yeast arrestin-related protein Bul1 is a novel actor of glucose-induced endocytosis

International audienc

Multilevel regulation of an α-arrestin by glucose depletion controls hexose transporter endocytosis

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A ribosome-anchored chaperone network that facilitates eukaryotic ribosome biogenesis

Ribosome-anchored proteins Jjj1 and Zuo1 function together with Hsp70 to mediate ribosome biogenesis (see also the companion paper from Koplin et al. in this issue)

Heterozygous Yeast Deletion Collection Screens Reveal Essential Targets of Hsp90

Hsp90 is an essential eukaryotic chaperone with a role in folding specific “client” proteins such as kinases and hormone receptors. Previously performed homozygous diploid yeast deletion collection screens uncovered broad requirements for Hsp90 in cellular transport and cell cycle progression. These screens also revealed that the requisite cellular functions of Hsp90 change with growth temperature. We present here for the first time the results of heterozygous deletion collection screens conducted at the hypothermic stress temperature of 15°C. Extensive bioinformatic analyses were performed on the resulting data in combination with data from homozygous and heterozygous screens previously conducted at normal (30°C) and hyperthermic stress (37°C) growth temperatures. Our resulting meta-analysis uncovered extensive connections between Hsp90 and (1) general transcription, (2) ribosome biogenesis and (3) GTP binding proteins. Predictions from bioinformatic analyses were tested experimentally, supporting a role for Hsp90 in ribosome stability. Importantly, the integrated analysis of the 15°C heterozygous deletion pool screen with previously conducted 30°C and 37°C screens allows for essential genetic targets of Hsp90 to emerge. Altogether, these novel contributions enable a more complete picture of essential Hsp90 functions

An electrostatic switching mechanism to control the lipid transfer activity of Osh6p

International audienceA central assumption is that lipid transfer proteins (LTPs) bind transiently to organelle membranes to distribute lipids in the eukaryotic cell. Osh6p and Osh7p are yeast LTPs that transfer phosphatidylserine (PS) from the endoplasmic reticulum (ER) to the plasma membrane (PM) via PS/phosphatidylinositol-4-phosphate (PI4P) exchange cycles. It is unknown how, at each cycle, they escape from the electrostatic attraction of the PM, highly anionic, to return to the ER. Using cellular and in vitro approaches, we show that Osh6p reduces its avidity for anionic membranes once it captures PS or PI4P, due to a molecular lid closing its lipid-binding pocket. Thus, Osh6p maintains its transport activity between ER- and PM-like membranes. Further investigations reveal that the lid governs the membrane docking and activity of Osh6p because it is anionic. Our study unveils how an LTP self-limits its residency time on membranes, via an electrostatic switching mechanism, to transfer lipids efficiently

Osh6 requires Ist2 for localization to the ER-PM contacts and efficient phosphatidylserine transport

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Ubc13–Mms2 cooperates with a family of RING E3 proteins in budding yeast membrane protein sorting

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A comprehensive library of fluorescent constructs of SARS‐CoV‐2 proteins and their initial characterisation in different cell types

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Systematic Functional Prioritization of Protein Posttranslational Modifications

Protein function is often regulated by post-translational modifications (PTMs) and recent advances in mass-spectrometry have resulted in an exponential increase in PTM identification. However, the functional significance of the vast majority of these modifications remains unknown. To address this problem, we compiled nearly 200,000 phosphorylation, acetylation and ubiquitination sites from 11 eukaryotic species, including 2,500 novel ubiquitylation sites for S. cerevisiae. We developed methods to prioritize the functional relevance of these PTMs by predicting those that likely participate in cross-regulatory events, regulate domain activity or mediate protein-protein interactions. PTM conservation within domain families identifies regulatory ‘hot-spots’ that overlap with functionally important regions, a concept we experimentally validated on the HSP70 domain family. Finally, our analysis of the evolution of PTM regulation highlights potential routes for neutral drift in regulatory interactions and suggests that only a fraction of modification sites are likely to have a significant biological role