scholarly journals Genetic Analysis of the TOR Pathway in Aspergillus nidulans

2005 ◽  
Vol 4 (9) ◽  
pp. 1595-1598 ◽  
Author(s):  
Gregory J. Fitzgibbon ◽  
Igor Y. Morozov ◽  
Meriel G. Jones ◽  
Mark X. Caddick
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Genetic Analysis ◽  
Aspergillus Nidulans ◽  
Minor Role ◽  
Tor Signaling ◽  
Tor Pathway ◽  
Genes Encoding ◽  
Tor Kinase ◽  
Mutant Phenotypes ◽  
A Minor

ABSTRACT We identified five genes encoding components of the TOR signaling pathway within Aspergillus nidulans. Unlike the situation in Saccharomyces cerevisiae, there is only a single Tor kinase, as in plant and animal systems, and mutant phenotypes suggest that the TOR pathway plays only a minor role in regulating nitrogen metabolism.

scholarly journals 40S ribosome profiling reveals distinct roles for Tma20/Tma22 (MCT-1/DENR) and Tma64 (eIF2D) in 40S subunit recycling

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
David J. Young ◽  
Sezen Meydan ◽  
Nicholas R. Guydosh
Keyword(s):  
Protein Synthesis ◽  
Neurological Disease ◽  
Ribosome Profiling ◽  
Minor Role ◽  
Stop Codons ◽  
Genes Encoding ◽  
Ribosome Footprinting ◽  
A Minor ◽  
And Control ◽  
In Cells

AbstractThe recycling of ribosomes at stop codons for use in further rounds of translation is critical for efficient protein synthesis. Removal of the 60S subunit is catalyzed by the ATPase Rli1 (ABCE1) while removal of the 40S is thought to require Tma64 (eIF2D), Tma20 (MCT-1), and Tma22 (DENR). However, it remains unclear how these Tma proteins cause 40S removal and control reinitiation of downstream translation. Here we used a 40S ribosome footprinting strategy to directly observe intermediate steps of ribosome recycling in cells. Deletion of the genes encoding these Tma proteins resulted in broad accumulation of unrecycled 40S subunits at stop codons, directly establishing their role in 40S recycling. Furthermore, the Tma20/Tma22 heterodimer was responsible for a majority of 40S recycling events while Tma64 played a minor role. Introduction of an autism-associated mutation into TMA22 resulted in a loss of 40S recycling activity, linking ribosome recycling and neurological disease.

Dominant effects of tubulin overexpression in Saccharomyces cerevisiae

1989 ◽  
Vol 9 (3) ◽  
pp. 1049-1059
Author(s):  
D Burke ◽  
P Gasdaska ◽  
L Hartwell
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chromosome Loss ◽  
Beta Tubulin ◽  
Alpha Tubulin ◽  
Inducible Promoters ◽  
Selective Degradation ◽  
Novel Structure ◽  
Genes Encoding ◽  
Transient Overexpression ◽  
Mutant Phenotypes

The consequences of altering the levels of alpha- and beta-tubulin in Saccharomyces cerevisiae were examined by constructing fusions of the structural genes encoding the tubulins to strong galactose-inducible promoters. Overexpression of beta-tubulin (TUB2) was lethal: cells arrested in the G2 stage of the cell cycle exhibited an increased frequency of chromosome loss, were devoid of microtubules, and accumulated beta-tubulin in a novel structure. Overexpression of the major alpha-tubulin gene (TUB1) was not lethal and did not affect chromosome segregation. The rate of alpha-tubulin mRNA and protein synthesis was increased, but the protein did not accumulate. Overexpression of both alpha- and beta-tubulin together resulted in arrested cell division, and cells accumulated excess tubules that contained both alpha- and beta-tubulin. Transient overexpression of both tubulins resulted in a high frequency of chromosome loss. These data suggest that strong selective pressure exists to prevent excess accumulation of microtubules or beta-tubulin and suggest a model by which this goal may be achieved by selective degradation of unassembled alpha-tubulin. Furthermore, the phenotype of beta-tubulin overexpression is similar to the phenotype of a beta-tubulin deficiency. These results add to a number of recent studies demonstrating that mutant phenotypes generated by overexpression can be informative about the function of the gene product.

scholarly journals Diversity, Epidemiology, and Genetics of Class D β-Lactamases

2009 ◽  
Vol 54 (1) ◽  
pp. 24-38 ◽  
Author(s):  
Laurent Poirel ◽  
Thierry Naas ◽  
Patrice Nordmann
Keyword(s):  
Natural Resistance ◽  
Minor Role ◽  
Insertion Sequences ◽  
Class 1 Integron ◽  
Gram Negative ◽  
Class D ◽  
Class 1 ◽  
Great Heterogeneity ◽  
Genes Encoding ◽  
A Minor

ABSTRACT Class D β-lactamase-mediated resistance to β-lactams has been increasingly reported during the last decade. Those enzymes also known as oxacillinases or OXAs are widely distributed among Gram negatives. Genes encoding class D β-lactamases are known to be intrinsic in many Gram-negative rods, including Acinetobacter baumannii and Pseudomonas aeruginosa, but play a minor role in natural resistance phenotypes. The OXAs (ca. 150 variants reported so far) are characterized by an important genetic diversity and a great heterogeneity in terms of β-lactam hydrolysis spectrum. The acquired OXAs possess either a narrow spectrum or an expanded spectrum of hydrolysis, including carbapenems in several instances. Acquired class D β-lactamase genes are mostly associated to class 1 integron or to insertion sequences.

scholarly journals Shugoshin Promotes Sister Kinetochore Biorientation in Saccharomyces cerevisiae

2008 ◽  
Vol 19 (3) ◽  
pp. 1199-1209 ◽  
Author(s):  
Brendan M. Kiburz ◽  
Angelika Amon ◽  
Adele L. Marston
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chromosome Segregation ◽  
Minor Role ◽  
Meiotic Cell ◽  
Homologous Chromosomes ◽  
Cell Divisions ◽  
Sister Chromatids ◽  
Sister Kinetochore ◽  
A Minor ◽  
Meiosis I

Chromosome segregation must be executed accurately during both mitotic and meiotic cell divisions. Sgo1 plays a key role in ensuring faithful chromosome segregation in at least two ways. During meiosis this protein regulates the removal of cohesins, the proteins that hold sister chromatids together, from chromosomes. During mitosis, Sgo1 is required for sensing the absence of tension caused by sister kinetochores not being attached to microtubules emanating from opposite poles. Here we describe a differential requirement for Sgo1 in the segregation of homologous chromosomes and sister chromatids. Sgo1 plays only a minor role in segregating homologous chromosomes at meiosis I. In contrast, Sgo1 is important to bias sister kinetochores toward biorientation. We suggest that Sgo1 acts at sister kinetochores to promote their biorientation.

Nuclear behaviour and cell wall composition in relation to budding in mutants of the yeast Saccharomyces cerevisiae

1986 ◽  
Vol 64 (1) ◽  
pp. 193-200 ◽  
Author(s):  
Mario Lachapelle ◽  
E. Roger Boothroyd
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Spindle Pole ◽  
Minor Role ◽  
Temperature Sensitive ◽  
Yeast Saccharomyces Cerevisiae ◽  
Bud Emergence ◽  
Spindle Elongation ◽  
10 Nm Filaments ◽  
A Minor

A temperature-sensitive, cell division cycle mutant (cdc24–1) and karyogamy-deficient (kar1) mutant of Saccharomyces cerevisiae, both of which can produce binucleate or multinucleate cells, were used to study certain aspects of budding, after fluorescent staining for mannan, chitin, and nuclei (DNA). In most binucleate cells the two nuclei lay close together and divided into the same bud. In a few, however, the nuclei were far apart and one or two buds were formed, each proximal to a nucleus. The proximity of daughter nuclei in most blocked cdc24–1 cells suggests a role for the CDC24 gene product in spindle elongation. The relationship between the nuclei and the number and location of buds supports the theory of a preponderant role for the nucleus in budding. Although buds develop preferentially in regions of low chitin content in kar1 heterokaryons, the ability of cdc24–1 cells to bud even with a uniformly high content of chitin and mannan suggests a minor role for these cell wall constituents in determining the sites of bud emergence. The chitin ring is not needed for bud emergence but seems to play a role in normal bud development and in septum formation. Electron microscopy of cdc24–1 cells blocked (37 °C) for 8 h and released (23 °C) for 30 min showed morphologically normal spindle pole bodies, cytoplasmic microtubules, and intranuclear spindles. Although the chitin ring was absent, the ring of 10-nm filaments was present, consistent with its proposed role in bud emergence.

scholarly journals C-terminal HA tags compromise function and exacerbate phenotypes of Saccharomyces cerevisiae Bloom’s helicase homolog Sgs1 SUMOylation-associated mutants

2020 ◽  
Author(s):  
Matan Cohen ◽  
Michael Lichten
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Mitotic Cell ◽  
Minor Role ◽  
Mitotic Cell Cycle ◽  
Human Influenza ◽  
Wild Type ◽  
Epitope Tag ◽  
Influenza Hemagglutinin ◽  
A Minor

AbstractThe Sgs1 helicase and Top3-Rmi1 decatenase form a complex that affects homologous recombination outcomes during the mitotic cell cycle and during meiosis. Previous studies have reported that Sgs1-Top3-Rmi1 function is regulated by SUMOylation that is catalyzed by the Smc5-Smc6-Mms21 complex. These studies used strains in which SGS1 was C-terminally tagged with three or six copies of a human influenza hemagglutinin-derived epitope tag (3HA and 6HA). They identified SGS1 mutants that affect its SUMOylation, which we will refer to as SGS1 SUMO-site mutants. In previous work, these mutants showed phenotypes consistent with substantial loss of Sgs1-Top3-Rmi1 function during the mitotic cell cycle. We find that the reported phenotypes are largely due to the presence of the HA epitope tags. Untagged SGS1 SUMO-site mutants show either wild-type or weak hypomorphic phenotypes, depending on the assay. These phenotypes are exacerbated by both 6HA and 3HA epitope tags in two different S. cerevisiae strain backgrounds. Importantly, a C-terminal 6HA tag confers strong hypomorphic or null phenotypes on an otherwise wild-type Sgs1 protein. Taken together, these results suggest that the HA epitope tags used in previous studies seriously compromise Sgs1 function. Furthermore, they raise the possibilities either that sufficient SUMOylation of the Sgs1-Top3-Rmi1 complex might still occur in the SUMO-site mutants isolated, or that Smc5-Smc6-Mms21-mediated SUMOylation plays a minor role in the regulation of Sgs1-Top3-Rmi1 during recombination.

scholarly journals Mec1 and Rad53 Inhibit Formation of Single-Stranded DNA at Telomeres of Saccharomyces cerevisiae cdc13-1 Mutants

Genetics ◽  
2004 ◽  
Vol 166 (2) ◽  
pp. 753-764 ◽  
Author(s):  
Xindan Jia ◽  
Ted Weinert ◽  
David Lydall
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Budding Yeast ◽  
Minor Role ◽  
Clamp Loader ◽  
Checkpoint Proteins ◽  
Checkpoint Kinases ◽  
Sliding Clamp ◽  
Telomere Binding Protein ◽  
A Minor ◽  
Dependent Pathway

Abstract Here we examine the roles of budding-yeast checkpoint proteins in regulating degradation of dsDNA to ssDNA at unprotected telomeres (in Cdc13 telomere-binding protein defective strains). We find that Rad17, Mec3, as well as Rad24, members of the putative checkpoint clamp loader (Rad24) and sliding clamp (Rad17, Mec3) complexes, are important for promoting degradation of dsDNA in and near telomere repeats. We find that Mec1, Rad53, as well as Rad9, have the opposite role: they inhibit degradation. Downstream checkpoint kinases Chk1 and Dun1 play no detectable role in either promoting degradation or inhibiting it. These data suggest, first, that the checkpoint sliding clamp regulates and/or recruits some nucleases for degradation, and, second, that Mec1 activates Rad9 to activate Rad53 to inhibit degradation. Further analysis shows that Rad9 inhibits ssDNA generation by both Mec1/Rad53-dependent and -independent pathways. Exo1 appears to be targeted by the Mec1/Rad53-dependent pathway. Finally, analysis of double mutants suggests a minor role for Mec1 in promoting Rad24-dependent degradation of dsDNA. Thus, checkpoint proteins orchestrate carefully ssDNA production at unprotected telomeres.

scholarly journals Relative Contribution of the ABC Transporters Cdr1, Pdh1, and Snq2 to Azole Resistance inCandida glabrata

2018 ◽  
Vol 62 (10) ◽  
Author(s):  
Sarah G. Whaley ◽  
Qing Zhang ◽  
Kelly E. Caudle ◽  
P. David Rogers
Keyword(s):  
Multidrug Resistance ◽  
Minor Role ◽  
Azole Resistance ◽  
Content Type ◽  
Azole Antifungals ◽  
Zinc Cluster ◽  
Relative Contribution ◽  
Genes Encoding ◽  
High Level ◽  
A Minor

ABSTRACTThe utility of the azole antifungals for the treatment of invasive candidiasis is severely hampered by azole resistance inCandida glabrata. This resistance is mediated almost exclusively by activating mutations in the zinc cluster transcription factor Pdr1, which controls the genes encoding the multidrug resistance transporters Cdr1, Pdh1, and Snq2. However, the specific relative contributions of these transporters to resistance are not known. To address this question, theSAT1flipper method was used to deleteCDR1,PDH1, andSNQ2in a strain ofC. glabrataengineered to carry a clinically relevant activating mutation inPDR1. Susceptibility testing was performed according to the CLSI guidelines, with minor modifications, and confirmed with Etest strips. Of the single-transporter-deletion strains, only theCDR1deletion resulted in a decreased azole MIC. The deletion ofPDH1in combination withCDR1resulted in a moderate decrease in MIC compared to that observed with the deletion ofCDR1alone.SNQ2deletion only decreased the MIC in the triple-deletion strain in the absence of bothCDR1andPDH1. The deletion of all three transporters in combination decreased the MIC to the level observed in thePDR1deletion strains for some, but not all, azoles tested, which indicates that additional Pdr1 targets likely play a minor role in this process. These results indicate that while Cdr1 is the most important Pdr1-mediated multidrug resistance transporter for azole resistance in this clinical isolate, all three of these transporters contribute to its high-level resistance to the azole antifungals.

scholarly journals Dominant effects of tubulin overexpression in Saccharomyces cerevisiae.

1989 ◽  
Vol 9 (3) ◽  
pp. 1049-1059 ◽  
Author(s):  
D Burke ◽  
P Gasdaska ◽  
L Hartwell
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chromosome Loss ◽  
Beta Tubulin ◽  
Alpha Tubulin ◽  
Inducible Promoters ◽  
Selective Degradation ◽  
Novel Structure ◽  
Genes Encoding ◽  
Transient Overexpression ◽  
Mutant Phenotypes

The consequences of altering the levels of alpha- and beta-tubulin in Saccharomyces cerevisiae were examined by constructing fusions of the structural genes encoding the tubulins to strong galactose-inducible promoters. Overexpression of beta-tubulin (TUB2) was lethal: cells arrested in the G2 stage of the cell cycle exhibited an increased frequency of chromosome loss, were devoid of microtubules, and accumulated beta-tubulin in a novel structure. Overexpression of the major alpha-tubulin gene (TUB1) was not lethal and did not affect chromosome segregation. The rate of alpha-tubulin mRNA and protein synthesis was increased, but the protein did not accumulate. Overexpression of both alpha- and beta-tubulin together resulted in arrested cell division, and cells accumulated excess tubules that contained both alpha- and beta-tubulin. Transient overexpression of both tubulins resulted in a high frequency of chromosome loss. These data suggest that strong selective pressure exists to prevent excess accumulation of microtubules or beta-tubulin and suggest a model by which this goal may be achieved by selective degradation of unassembled alpha-tubulin. Furthermore, the phenotype of beta-tubulin overexpression is similar to the phenotype of a beta-tubulin deficiency. These results add to a number of recent studies demonstrating that mutant phenotypes generated by overexpression can be informative about the function of the gene product.

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