Publications by authors named "François Doignon"

16 Publications

  • Page 1 of 1

Assignment of H, C and N resonances and secondary structure of the Rgd1-RhoGAP domain.

Biomol NMR Assign 2018 04 26;12(1):129-132. Epub 2017 Dec 26.

Chimie et Biologie des Membranes et des Nano-objets, Université de Bordeaux, CNRS UMR 5248, Allée Geoffroy Saint Hilaire, 33600, Pessac Cedex, France.

The protein Rgd1 is involved in the regulation of cytoskeleton formation and in signalling pathways that control cell polarity and growth in Saccharomyces cerevisiae. Rgd1p is composed of a F-BAR domain required for membrane binding and a RhoGAP domain responsible for activating Rho3p and Rho4p, two GTPases respectively involved in bud growth and cytokinesis. Rgd1p is recruited to the membrane through interactions with phosphoinositide lipids, which bind the two isolated domains and stimulate the RhoGAP activity on Rho4p. As previously shown by crystallography, the membrane-binding F-BAR domain contains a conserved inositol phosphate binding site, which explains the preferential binding of phosphoinositides. In contrast, RhoGAP domains are not expected to bind lipids. In order to unravel this puzzling feature, we solved the three-dimensional structure of the isolated protein and found a cryptic phosphoinositide binding site involving non conserved residues (Martinez et al. 2017). The assignment of the resonances and secondary structure of Rgd1-RhoGAP (aa 450-666) is presented here.
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http://dx.doi.org/10.1007/s12104-017-9794-zDOI Listing
April 2018

Structural evidence of a phosphoinositide-binding site in the Rgd1-RhoGAP domain.

Biochem J 2017 09 20;474(19):3307-3319. Epub 2017 Sep 20.

Université de Bordeaux, Chimie et Biologie des Membranes et des Nano-objets, CNRS UMR 5248, Allée Geoffroy Saint Hilaire, 33600 Pessac Cedex, France

Phosphoinositide lipids recruit proteins to the plasma membrane involved in the regulation of cytoskeleton organization and in signalling pathways that control cell polarity and growth. Among those, Rgd1p is a yeast GTPase-activating protein (GAP) specific for Rho3p and Rho4p GTPases, which control actin polymerization and stress signalling pathways. Phosphoinositides not only bind Rgd1p, but also stimulate its GAP activity on the membrane-anchored form of Rho4p. Both F-BAR (F-BAR FCH, and BAR) and RhoGAP domains of Rgd1p are involved in lipid interactions. In the Rgd1p-F-BAR domain, a phosphoinositide-binding site has been recently characterized. We report here the X-ray structure of the Rgd1p-RhoGAP domain, identify by NMR spectroscopy and confirm by docking simulations, a new but cryptic phosphoinositide-binding site, comprising contiguous A1, A1' and B helices. The addition of helix A1', unusual among RhoGAP domains, seems to be crucial for lipid interactions. Such a site was totally unexpected inside a RhoGAP domain, as it was not predicted from either the protein sequence or its three-dimensional structure. Phosphoinositide-binding sites in RhoGAP domains have been reported to correspond to polybasic regions, which are located at the unstructured flexible termini of proteins. Solid-state NMR spectroscopy experiments confirm the membrane interaction of the Rgd1p-RhoGAP domain upon the addition of PtdIns(4,5)P and indicate a slight membrane destabilization in the presence of the two partners.
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http://dx.doi.org/10.1042/BCJ20170331DOI Listing
September 2017

Requirement of Phosphoinositides Containing Stearic Acid To Control Cell Polarity.

Mol Cell Biol 2016 02 28;36(5):765-80. Epub 2015 Dec 28.

Université Bordeaux, Laboratoire de Biogenèse Membranaire, UMR 5200, Bordeaux, France CNRS, Laboratoire de Biogenèse Membranaire, UMR 5200, Bordeaux, France.

Phosphoinositides (PIPs) are present in very small amounts but are essential for cell signaling, morphogenesis, and polarity. By mass spectrometry, we demonstrated that some PIPs with stearic acyl chains were strongly disturbed in a psi1Δ Saccharomyces cerevisiae yeast strain deficient in the specific incorporation of a stearoyl chain at the sn-1 position of phosphatidylinositol. The absence of PIPs containing stearic acid induced disturbances in intracellular trafficking, although the total amount of PIPs was not diminished. Changes in PIPs also induced alterations in the budding pattern and defects in actin cytoskeleton organization (cables and patches). Moreover, when the PSI1 gene was impaired, a high proportion of cells with bipolar cortical actin patches that occurred concomitantly with the bipolar localization of Cdc42p was specifically found among diploid cells. This bipolar cortical actin phenotype, never previously described, was also detected in a bud9Δ/bud9Δ strain. Very interestingly, overexpression of PSI1 reversed this phenotype.
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http://dx.doi.org/10.1128/MCB.00843-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4760214PMC
February 2016

Helicobacter pullorum cytolethal distending toxin targets vinculin and cortactin and triggers formation of lamellipodia in intestinal epithelial cells.

J Infect Dis 2014 Feb;209(4):588-99

Université de Bordeaux, Laboratoire de bactériologie, Centre National de Référence des Campylobacters et Hélicobacters.

Helicobacter pullorum, a bacterium initially isolated from poultry, has been associated with human digestive disorders. However, the factor responsible for its cytopathogenic effects on epithelial cells has not been formally identified. The cytopathogenic alterations induced by several human and avian H. pullorum strains were investigated on human intestinal epithelial cell lines. Moreover, the effects of the cytolethal distending toxin (CDT) were evaluated first by using a wild-type strain and its corresponding cdtB isogenic mutant and second by delivering the active CdtB subunit of the CDT directly into the cells. All of the H. pullorum strains induced cellular distending phenotype, actin cytoskeleton remodeling, and G2/M cell cycle arrest. These effects were dependent on the CDT, as they were (1) not observed in response to a cdtB isogenic mutant strain and (2) present in cells expressing CdtB. CdtB also induced an atypical delocalization of vinculin from focal adhesions to the perinuclear region, formation of cortical actin-rich large lamellipodia with an upregulation of cortactin, and decreased cellular adherence. In conclusion, the CDT of H. pullorum is responsible for major cytopathogenic effects in vitro, confirming its role as a main virulence factor of this emerging human pathogen.
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http://dx.doi.org/10.1093/infdis/jit539DOI Listing
February 2014

The Saccharomyces cerevisiae RhoGAP Rgd1 is phosphorylated by the Aurora B like kinase Ipl1.

Biochem Biophys Res Commun 2013 Mar 27;433(1):1-5. Epub 2013 Feb 27.

Univ. Bordeaux, Institut de Biochimie et Génétique Cellulaires, UMR CNRS 5095, F-33000 Bordeaux, France.

Polarized growth of the yeast Saccharomyces cerevisiae depends on different biological processes and requires several signaling pathways. Signaling is mediated through a set of proteins, which include Rho3p and Rho4p GTPases. Although these two proteins are involved in the control of distinct aspects of polarized growth in yeast, they have a common regulator: the Rgd1 RhoGAP protein. Here we demonstrate that Rgd1p is phosphorylated by the Aurora B like kinase Ipl1 and we observe that loss of Ipl1 function leads to a new Rgd1p distribution in a small part of the cell population.
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http://dx.doi.org/10.1016/j.bbrc.2013.02.081DOI Listing
March 2013

Secretory pathway-dependent localization of the Saccharomyces cerevisiae Rho GTPase-activating protein Rgd1p at growth sites.

Eukaryot Cell 2012 May 23;11(5):590-600. Epub 2012 Mar 23.

Université de Bordeaux, Institut de Biochimie et de Génétique Cellulaires and CNRS, UMR 5095, Bordeaux, France.

Establishment and maintenance of cell polarity in eukaryotes depends upon the regulation of Rho GTPases. In Saccharomyces cerevisiae, the Rho GTPase activating protein (RhoGAP) Rgd1p stimulates the GTPase activities of Rho3p and Rho4p, which are involved in bud growth and cytokinesis, respectively. Consistent with the distribution of Rho3p and Rho4p, Rgd1p is found mostly in areas of polarized growth during cell cycle progression. Rgd1p was mislocalized in mutants specifically altered for Golgi apparatus-based phosphatidylinositol 4-P [PtdIns(4)P] synthesis and for PtdIns(4,5)P(2) production at the plasma membrane. Analysis of Rgd1p distribution in different membrane-trafficking mutants suggested that Rgd1p was delivered to growth sites via the secretory pathway. Rgd1p may associate with post-Golgi vesicles by binding to PtdIns(4)P and then be transported by secretory vesicles to the plasma membrane. In agreement, we show that Rgd1p coimmunoprecipitated and localized with markers specific to secretory vesicles and cofractionated with a plasma membrane marker. Moreover, in vivo imaging revealed that Rgd1p was transported in an anterograde manner from the mother cell to the daughter cell in a vectoral manner. Our data indicate that secretory vesicles are involved in the delivery of RhoGAP Rgd1p to the bud tip and bud neck.
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http://dx.doi.org/10.1128/EC.00042-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3346426PMC
May 2012

Evidence for specific interaction between the RhoGAP domain from the yeast Rgd1 protein and phosphoinositides.

Biochem Biophys Res Commun 2011 Feb 5;405(1):74-8. Epub 2011 Jan 5.

Université de Bordeaux, Chimie et Biologie des Membranes et des Nanoobjets, CNRS UMR 5248, Pessac, France.

The Rho GTPase activating protein Rgd1 increases the GTPase activity of Rho3p and Rho4p, which are involved in bud growth and cytokinesis, respectively, in the budding yeast Saccharomyces cerevisiae. Rgd1p is a member of the F-BAR family conserved in eukaryotes; indeed, in addition to the C-terminal RhoGAP domain Rgd1p possesses an F-BAR domain at its N-terminus. Phosphoinositides discriminate between the GTPase activities of Rho3p and Rho4p through Rgd1p and specifically stimulate the RhoGAP activity of Rgd1p on Rho4p. Determining specific interactions and resolving the structure of Rgd1p should provide insight into the functioning of this family of protein. We report the preparation of highly pure and functional RhoGAP domain of Rgd1 RhoGAP domain using a high yield expression procedure. By gel filtration and circular dichroïsm we provide the first evidences for a specific interaction between a RhoGAP domain (the RhoGAP domain of Rgd1p) and phosphoinositides.
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http://dx.doi.org/10.1016/j.bbrc.2010.12.130DOI Listing
February 2011

Evidence for functional links between the Rgd1-Rho3 RhoGAP-GTPase module and Tos2, a protein involved in polarized growth in Saccharomyces cerevisiae.

FEMS Yeast Res 2011 Mar 8;11(2):179-91. Epub 2010 Dec 8.

RDPR, Institute of Cellular Biochemistry and Genetics, University of Bordeaux 2, Bordeaux, France.

The Rho GTPase-activating protein Rgd1p positively regulates the GTPase activity of Rho3p and Rho4p, which are involved in bud growth and cytokinesis, respectively, in the budding yeast Saccharomyces cerevisiae. Two-hybrid screening identified Tos2p as a candidate Rgd1p-binding protein. Further analyses confirmed that Tos2p binds to the RhoGAP Rgd1p through its C-terminal region. Both Tos2p and Rgd1p are localized to polarized growth sites during the cell cycle and associated with detergent-resistant membranes. We observed that TOS2 overexpression suppressed rgd1Δ sensitivity to a low pH. In the tos2Δ strain, the amount of GTP-bound Rho3p was increased, suggesting an influence of Tos2p on Rgd1p activity in vivo. We also showed a functional interaction between the TOS2 and the RHO3 genes: TOS2 overexpression partially suppressed the growth defect of rho3-V51 cells at a restrictive temperature. We propose that Tos2p, a protein involved in polarized growth and most probably associated with the plasma membrane, modulates the action of Rgd1p and Rho3p in S. cerevisiae.
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http://dx.doi.org/10.1111/j.1567-1364.2010.00704.xDOI Listing
March 2011

The Candida albicans Rgd1 is a RhoGAP protein involved in the control of filamentous growth.

Fungal Genet Biol 2010 Dec 15;47(12):1001-11. Epub 2010 Jul 15.

Université de Bordeaux, Institut de Biochimie et Génétique Cellulaires, Bordeaux, France.

Rho proteins are essential regulators of polarized growth in eukaryotic cells. These proteins are down-regulated in vivo by specific Rho GTPase Activating Proteins (RhoGAP). We investigated the role of Rgd1 RhoGAP, encoded by the Candida albicans RGD1 gene. We demonstrated that CaCdc42, CaRho3 and CaRho4 proteins had an intrinsic GTPase activity and that CaRgd1 stimulates in vitro GTP hydrolysis of these GTPases. Deletion of RGD1 in C. albicans results in sensitivity to low pH as already described for rgd1Δ in Saccharomyces cerevisiae. The role of Rgd1 in survival at low pH is conserved in the two yeast species as the CaRGD1 gene complements the Scrgd1Δ sensitivity. By tagging the RhoGAP with GFP, we found that CaRgd1 is localized at the tip and cortex of growing cells and during cytokinesis at the septation sites in yeast and filamentous forms. We investigated the effect of CaRgd1 on the control of the polarized growth. Removing CaRGD1 alleles increased filamentous growth and cells lacking CaRgd1 presented longer germ tubes. Conversely, RGD1 overexpression restricted hyphae growth. Our results demonstrate that Rgd1 is critical for filamentous formation in C. albicans especially for filamentous elongation.
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http://dx.doi.org/10.1016/j.fgb.2010.07.007DOI Listing
December 2010

Through its F-BAR and RhoGAP domains, Rgd1p acts in different polarized growth processes in budding yeast.

Commun Integr Biol 2009 ;2(2):120-2

Université de Bordeaux; Institut de Biochimie et de Génétique Cellulaires and CNRS; UMR 5095; Bordeaux, France.

Protein domain architecture can be used to construct supramolecular structures, to carry out specific functions and to mediate signaling in prokaryotic and eukaryotic cells. The Rgd1p protein of budding yeast contains two domains with different functions in the cell: the F-BAR and RhoGAP domains. The F-BAR domain has been shown to interact with membrane phospholipids and is thought to induce or sense membrane curvature. The RhoGAP domain activates the GTP hydrolysis of two Rho GTPases, thereby regulating different cellular pathways. Specific molecular interactions with the F-BAR and RhoGAP domains, cell signaling and interplay between these domains may allow the Rgd1p protein to act in several different biological processes, all of which are required for polarized growth in yeast.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2686362PMC
http://dx.doi.org/10.4161/cib.7737DOI Listing
July 2011

Phosphoinositides affect both the cellular distribution and activity of the F-BAR-containing RhoGAP Rgd1p in yeast.

J Biol Chem 2008 Nov 9;283(48):33249-57. Epub 2008 Oct 9.

Université de Bordeaux, Institut de Biochimie et de Génétique Cellulaires, Bordeaux, F-33076 France.

Cell polarity is a key element of development in most eukaryotes. The Rho GTPase-activating protein Rgd1p positively regulates the GTPase activity of Rho3p and Rho4p, which are involved in bud growth and cytokinesis, respectively, in the budding yeast Saccharomyces cerevisiae. Rgd1p contains an F-BAR domain at its N-terminal end in addition to its RhoGAP domain at its C-terminal end. We demonstrate here that phospholipids discriminate between the GTPase activities of Rho3p and Rho4p through Rgd1p and specifically stimulate the RhoGAP activity on Rho4p. The central region of the protein contiguous to the F-BAR domain is required for this stimulation. The F-BAR region binds to phosphoinositides in vitro and also plays a key role in the localization of Rgd1p to the bud tip and neck during the cell cycle. Studies of heat-sensitive mutants lacking phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-biphosphate suggested that Rgd1p initially binds to Golgi membranes via phosphatidylinositol 4-phosphate and is then transported to the plasma membrane, where it binds phosphatidylinositol 4,5-biphosphate. We demonstrate here the dual effects of phosphoinositides on a RhoGTPase-activating protein. Phosphoinositides both regulate the recruitment and trafficking of Rgd1p to membranes via the F-BAR domain and specifically stimulate GTPase-activating protein activity, consistent with functional interplay between lipids, RhoGAP, and its related GTPases in yeast growth.
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http://dx.doi.org/10.1074/jbc.M805161200DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2662255PMC
November 2008

The Rho3 and Rho4 small GTPases interact functionally with Wsc1p, a cell surface sensor of the protein kinase C cell-integrity pathway in Saccharomyces cerevisiae.

Microbiology (Reading) 2006 Mar;152(Pt 3):695-708

Laboratoire de Biologie Moléculaire et de Séquençage, Institut de Biochimie et Génétique Cellulaires, UMR Université Victor Segalen Bordeaux 2-CNRS 5095, box 64, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France.

Rgd1, a GTPase-activating protein, is the only known negative regulator of the Rho3 and Rho4 small GTPases in the yeast Saccharomyces cerevisiae. Rho3p and Rho4p are involved in regulating cell polarity by controlling polarized exocytosis. Co-inactivation of RGD1 and WSC1, which is a cell wall sensor-encoding gene, is lethal. Another plasma membrane sensor, Mid2p, is known to rescue the rgd1Deltawsc1Delta synthetic lethality. It has been proposed that Wsc1p and Mid2p act upstream of the protein kinase C (PKC) pathway to function as mechanosensors of cell wall stress. Analysis of the synthetic lethal phenomenon revealed that production of activated Rho3p and Rho4p leads to lethality in wsc1Delta cells. Inactivation of RHO3 or RHO4 was able to rescue the rgd1Deltawsc1Delta synthetic lethality, supporting the idea that the accumulation of GTP-bound Rho proteins, following loss of Rgd1p, is detrimental if the Wsc1 sensor is absent. In contrast, the genetic interaction between RGD1 and MID2 was not due to an accumulation of GTP-bound Rho proteins. It was proposed that simultaneous inactivation of RGD1 and WSC1 constitutively activates the PKC-mitogen-activated protein kinase (MAP kinase) pathway. Moreover, it was shown that the activity of this pathway was not involved in the synthetic lethal interaction, which suggests the existence of another mechanism. Consistent with this idea, it was found that perturbations in Rho3-mediated polarized exocytosis specifically impair the abundance and processing of Wsc1 and Mid2 proteins. Hence, it is proposed that Wsc1p participates in the regulation of a Rho3/4-dependent cellular mechanism, and that this is distinct from the role of Wsc1p in the PKC-MAP kinase pathway.
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http://dx.doi.org/10.1099/mic.0.28231-0DOI Listing
March 2006

The Rgd1p Rho GTPase-activating protein and the Mid2p cell wall sensor are required at low pH for protein kinase C pathway activation and cell survival in Saccharomyces cerevisiae.

Eukaryot Cell 2005 Aug;4(8):1375-86

Laboratoire de Biologie Moléculaire et de Séquençage, Institut de Biochimie et Génétique Cellulaires, UMR CNRS/Université Bordeaux 2, 5095, boite 64, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France.

The protein kinase C (PKC) pathway is involved in the maintenance of cell shape and cell integrity in Saccharomyces cerevisiae. Here, we show that this pathway mediates tolerance to low pH and that the Bck1 and Slt2 proteins belonging to the mitogen-activated protein kinase cascade are essential for cell survival at low pH. The PKC pathway is activated during acidification of the extracellular environment, and this activation depends mainly on the Mid2p cell wall sensor. Rgd1p, which encodes a Rho GTPase-activating protein for the small G proteins Rho3p and Rho4p, also plays a role in low-pH response. The rgd1Delta strain is sensitive to low pH, and Rgd1p activates the PKC pathway in an acidic environment. Inactivation of both genes in the double mutant rgd1Delta mid2Delta strain renders yeast cells unable to survive at low pH as in bck1Delta and slt2Delta strains. Our data provide evidence for the existence of two distinct ways, one involving Mid2p and the other involving Rgd1p, with both converging to the cell integrity pathway to mediate low-pH tolerance in Saccharomyces cerevisiae. Nevertheless, even if Rgd1p acts on the PKC pathway, it seems that its mediating action on low-pH tolerance is not limited to this pathway. As the Mid2p amount plays a role in rgd1Delta sensitivity to low pH, Mid2p seems to act more like a molecular rheostat, controlling the level of PKC pathway activity and thus allowing phenotypical expression of RGD1 inactivation.
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http://dx.doi.org/10.1128/EC.4.8.1375-1386.2005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1214525PMC
August 2005

RGD1, encoding a RhoGAP involved in low-pH survival, is an Msn2p/Msn4p regulated gene in Saccharomyces cerevisiae.

Gene 2005 May;351:159-69

Laboratoire de Biologie Moléculaire et de Séquençage, Institut de Biochimie et Génétique Cellulaires, UMR Université Victor Segalen Bordeaux 2-CNRS 5095, France.

The RhoGAP Rgd1p is involved in different signal transduction pathways in Saccharomyces cerevisiae through its regulatory activity upon the Rho3 and Rho4 GTPases. The rgd1Delta mutant, which presents a mortality at the entry into the stationary phase in minimal medium, is sensitive to medium acidification caused by biomass augmentation. We showed that low-pH shock leads to abnormal intracellular acidification of the rgd1Delta mutant. Transcriptional regulation of RGD1 was studied in several stress conditions and we observed an activation of RGD1 transcription at low pH and after heat and oxidative shocks. The transcription level at low pH and after heat shock was demonstrated to depend on the STRE box located in the RGD1 promoter. The general stress-activated transcription factors Msn2p and Msn4p as well as the HOG pathway were shown to mainly act on the basal RGD1 transcriptional level in normal and stress conditions.
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http://dx.doi.org/10.1016/j.gene.2005.03.034DOI Listing
May 2005

Glucose and trehalose PTS permeases of Spiroplasma citri probably share a single IIA domain, enabling the spiroplasma to adapt quickly to carbohydrate changes in its environment.

Microbiology (Reading) 2003 Sep;149(Pt 9):2687-2696

UMR Génomique Développement et Pouvoir Pathogène, IBVM, Centre INRA de Bordeaux, 71 avenue Edouard Bourlaux, BP 81, 33883 Villenave d'Ornon Cedex, France.

Spiroplasma citri is a plant-pathogenic mollicute phylogenetically related to Gram-positive bacteria. Spiroplasma cells are restricted to the phloem sieve tubes and are transmitted from plant to plant by the leafhopper vector Circulifer haematoceps. In the plant sieve tubes, S. citri grows on glucose and fructose, whereas in the leafhopper haemolymph the spiroplasma must grow on trehalose, the major sugar in insects. Previous studies in this laboratory have shown that fructose utilization was a key factor of spiroplasmal pathogenicity. To further study the implication of sugar metabolism in the interactions of S. citri with its plant host and its leafhopper vector, genes encoding permease enzymes II (EII(Glc) and EII(Tre)) of the S. citri phosphoenolpyruvate : glucose and phosphoenolpyruvate : trehalose phosphotransferase systems (PTS) were characterized. Mapping studies revealed that the EII(Glc) complex was split into two distinct polypeptides, IIA(Glc) and IICB(Glc), encoded by two separate genes, crr and ptsG, respectively. As expected, S. citri polypeptides IIA(Glc) and IICB(Glc) were more phylogenetically related to their counterparts from Gram-positive than to those from Gram-negative bacteria. The trehalose operon consisted of three genes treR, treP and treA, encoding a transcriptional regulator, the PTS permease (EII(Tre)) and the amylase, respectively. However, in contrast to the fructose-PTS permease, which is encoded as a single polypeptide (IIABC(Fru)) containing the three domains A, B and C, the trehalose-PTS permease (IIBC(Tre)) lacks its own IIA domain. No trehalose-specific IIA could be identified in the spiroplasmal genome, suggesting that the IIBC(Tre) permease probably functions with the IIA(Glc) domain. In agreement with this statement, yeast two-hybrid system experiments revealed that the IIA(Glc) domain interacted not only with IIB(Glc) but also with the IIB(Tre) domain. The results are discussed with respect to the ability of the spiroplasma to adapt from the phloem sap of the host plant to the haemolymph and salivary gland cells of the insect vector.
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http://dx.doi.org/10.1099/mic.0.26336-0DOI Listing
September 2003

Functional interactions between the VRP1-LAS17 and RHO3-RHO4 genes involved in actin cytoskeleton organization in Saccharomyces cerevisiae.

Curr Genet 2002 Feb 29;40(5):317-25. Epub 2002 Jan 29.

Laboratoire de Biologie Moléculaire et Séquençage, IBGC, UMR Université Victor Segalen Bordeaux 2-CNRS 5095, 146 rue Léo Saignat, BP 64, 33076 Bordeaux, France.

The RGD1 gene from Saccharomyces cerevisiae, which encodes a GTPase-activating protein for the Rho3 and Rho4 small G proteins, exhibits synthetic lethality with the VRP1 and LAS17 genes. Their products are proline-rich proteins that interact with both actin and myosins to ensure polarized growth. By testing functional links, we found that the VRP1 and LAS17 genes are potent suppressors of the rho3Delta mutation. In particular, they restore the polarization of actin patches in rho3Delta cells. Moreover, the vrp1Delta and las17Delta mutations were found to display a similar pattern of genetic interactions with specific actin-linked genes. These mutations also increase the sensitivity to activated forms of both Rho3p and Rho4p. These data support our working model, in which the VRP1 and LAS17 genes define a cellular complex that works in concert with the RHO3-RHO4 signaling pathway in yeast polarized growth. In addition, other observations lead us to propose that Rvs167p may act as a linking protein between the two cellular elements.
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http://dx.doi.org/10.1007/s00294-001-0268-5DOI Listing
February 2002
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