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Histone residues play an essential role in the regulation of various biological processes. In the present study, we utilized the H3/H4 histone mutant library to probe the functional aspects of histone residues in amino acid biosynthesis. We found that the histone residue H3R72 plays a crucial role in the regulation of isoleucine biosynthesis. Substitution of the arginine residue (H3R72) of histone H3 to alanine (H3R72A) renders yeast cells unable to grow in minimal medium. Histone mutant H3R72A requires external supplementation of either isoleucine, serine, or threonine for growth in minimal medium. We also observed that the H3R72 residue and leucine amino acid in synthetic complete medium might play a crucial role in determining the intake of isoleucine and threonine in yeast. Furthermore, gene deletion analysis of ILV1 and CHA1 in the H3R72A mutant confirmed that isoleucine is the sole requirement for growth in minimal medium. Altogether, we have identified that histone H3R72 residue may be crucial for yeast growth in minimal medium by regulating isoleucine biosynthesis through the Ilv1 enzyme in the budding yeast Saccharomyces cerevisiae. Key words: yeast, metabolism, histone, amino acids, epigenetics, isoleucine. Les résidus d'acides aminés des histones jouent un rôle essentiel dans la régulation de divers processus biologiques. Dans la présente étude, les auteurs ont utilisé une banque de mutants d'histones H3/H4 pour sonder les aspects fonctionnels des résidus d'acides aminés d'histones dans la biosynthèse des acides aminés. Ils ont découvert que le résidu d'histone H3R72 joue un rôle clé dans la régulation de la biosynthèse de l'isoleucine. La substitution du résidu arginine (H3R72) de l'histone H3 par une alanine (H3R72A) rend les cellules de levure incapables de croître en milieu minimal. Le mutant d'histone H3R72A nécessite un apport externe d'isoleucine, de sérine ou de thréonine pour croître en milieu minimal. Ils ont également observé que le résidu H3R72 et l'acide aminé leucine des milieux complets synthétiques pourraient jouer un rôle clé dans la détermination de l'apport d'isoleucine et de thréonine chez la levure. En outre, l'analyse de la délétion des genes ILV1 et CHA1 dans le mutant H3R72A confirmait que l'isoleucine est la seule exigence pour croître en milieu minimal. En somme, les auteurs ont déterminé que le résidu d'histone H3R72 peut être crucial pour la croissance de la levure en milieu minimal en régulant la biosynthèse de l'isoleucine par l'intermédiaire de l'enzyme Ilv1 chez la levure à bourgeonnement Saccharomyces cerevisiae. [Traduit par la Rédaction] Mots-clés : levure, métabolisme, histone, acides aminés, épigénétique, isoleucine., 1. Introduction The easy gene manipulation and availability of knockout gene libraries in yeast offer an excellent opportunity to understand biochemical pathways (Botstein and Fink 2011; Duina et al. 2014; [...]

A principal objective of cellular biology is to identify the function of proteins as they interact with their environment. Cellular localization provides context for the function and interactions of proteins. In this study, we seek to identify the localization of three proteins within Saccharomyces cerevisiae through C-terminal green fluorescent protein epitope tagging and subsequent fluorescent microscopy. As 75% of the yeast proteome has been classified, this project seeks to fill the remaining gap in unidentified cellular localization by investigating the proteins fsh3, gid10, and ade13. The analysis of high-resolution localization and comparative phylogenetic data reveals potential cellular environments and protein functions., Acknowledgements Sophia McNeill, Dr. Richard Adams, Dr. Indiren Pillay, and Dr. Ashok Hegde Recommended Citation Authors Lewis S. Barr (*), Georgia College and State University Follow Ellen France, Georgia College [...]

In the budding yeast Saccharomyces cerevisiae, self-recognition and the thereby promoted aggregation of thousands of cells into protective flocs is mediated by a family of cell-surface adhesins, the flocculins (Flo). Based on this social behavior FLO genes fulfill the definition of 'greenbeard' genes, which direct cooperation toward other carriers of the same gene. The process of flocculation plays an eminent role in the food industry for the production of beer and wine. However, the precise mode of flocculin-mediated surface recognition and the exact structure of cognate ligands have remained elusive. Here, we present structures of the adhesion domain of a flocculin complexed to its cognate ligands derived from yeast high-mannose oligosaccharides at resolutions up to 0.95 [Angstrom]. Besides a PA14-like architecture, the Flo5A domain reveals a previously undescribed lectin fold that utilizes a unique DcisD calcium-binding motif for carbohydrate binding and that is widely spread among pro- and eukaryotes. Given the high abundance of high-mannose oligosaccharides in yeast cell walls, the Flo5A structure suggests a model for recognition, where social non-self-instead of unsocial self-interactions are favored. altruism | molecular recognition | fungal development | atomic resolution doi: 10.1073/pnas.1013210108.

Cytokinesis in animal and fungal cells utilizes a contractile actomyosin ring (AMR). However, how myosin II is targeted to the division site and promotes AMR assembly, and how the AMR coordinates with membrane trafficking during cytokinesis, remains poorly understood. Here we show that Myo1 is a two-headed myosin II in Saccharomyces cerevisiae, and that Myo1 localizes to the division site via two distinct targeting signals in its tail that act sequentially during the cell cycle. Before cytokinesis, Myo1 localization depends on the septin-binding protein Bni5. During cytokinesis, Myo1 localization depends on the IQGAP Iqg1. We also show that the Myo1 tail is sufficient for promoting the assembly of a 'headless' AMR, which guides membrane deposition and extracellular matrix remodeling at the division site. Our study establishes a biphasic targeting mechanism for myosin II and highlights an underappreciated role of the AMR in cytokinesis beyond force generation. doi/ 10.1083/jcb.201005134

The parameters that control nuclear size and shape are poorly understood. In yeast, unregulated membrane proliferation, caused by deletion of the phospholipid biosynthesis inhibitor SPO7, leads to a single nuclear envelope 'flare' that protrudes into the cytoplasm. This flare is always associated with the asymmetrically localized nucleolus, which suggests that the site of membrane expansion is spatially confined by an unknown mechanism. Here we show that in spo7[DELTA] cells, mutations in vesicle-trafficking genes lead to multiple flares around the entire nucleus. These mutations also alter the distribution of small nucleolar RNA-associated nucleolar proteins independently of their effect on nuclear shape. Both single- and multi-flared nuclei have increased nuclear envelope surface area, yet they maintain the same nuclear/cell volume ratio as wild-type cells. These data suggest that, upon membrane expansion, the spatial confinement of the single nuclear flare is dependent on vesicle trafficking. Moreover, flares may facilitate maintenance of a constant nuclear/cell volume ratio in the face of altered membrane proliferation. doi/ 10.1083/jcb.201006083

Lte1 is known as a regulator of mitotic progression in budding yeast. Here we demonstrate phosphorylation-dependent inhibition of polarized bud growth during G2/M by Lte1. Cla4 activity first localizes Lte1 to the polarity cap and thus specifically to the bud. This localization is a prerequisite for subsequent Clb--Cdk-dependent phosphorylation of Lte1 and its relocalization to the entire bud cortex. There, Lte1 interferes with activation of the small GTPases, Ras and Bud1. The inhibition of Bud1 prevents untimely polarization until mitosis is completed and Cdc14 phosphatase is released. Inhibition of Bud1 and Ras depends on Lte1's GEF-like domain, which unexpectedly inhibits these small G proteins. Thus, Lte1 has dual functions for regulation of mitotic progression: it both induces mitotic exit and prevents polarized growth during mitotic arrest, thereby coupling cell cycle progression and morphological development. doi/ 10.1083/jcb.201005070

The discovery of large supramolecular complexes such as the purinosome suggests that subcellular organization is central to enzyme regulation. A screen of the yeast GFP strain collection to identify proteins that assemble into visible structures identified four novel filament systems comprised of glutamate synthase, guanosine diphosphate-mannose pyrophosphorylase, cytidine triphosphate (CTP) synthase, or subunits of the elF2/2B translation factor complex. Recruitment of CTP synthase to filaments and foci can be modulated by mutations and regulatory ligands that alter enzyme activity, arguing that the assembly of these structures is related to control of CTP synthase activity. CTP synthase filaments are evolutionarily conserved and are restricted to axons in neurons. This spatial regulation suggests that these filaments have additional functions separate from the regulation of enzyme activity. The identification of four novel filaments greatly expands the number of known intracellular filament networks and has broad implications for our understanding of how cells organize biochemical activities in the cytoplasm. doi/ 10.1083/jcb.201003001