scholarly journals A Nucleolar Protein That Affects Mating Efficiency in Saccharomyces cerevisiae by Altering the Morphological Response to Pheromone

Genetics ◽  
1998 ◽  
Vol 149 (2) ◽  
pp. 795-805
Author(s):  
Jinah Kim ◽  
Jeanne P Hirsch
Keyword(s):  
Growth Regulation ◽  
Subcellular Location ◽  
Null Alleles ◽  
Temperature Sensitive ◽  
Gene Products ◽  
Morphological Response ◽  
Mating Efficiency ◽  
Yeast Genes ◽  
Transcriptional Induction ◽  
In Cells

Abstract SSF1 and SSF2 are redundant essential yeast genes that, when overexpressed, increase the mating efficiency of cells containing a defective Ste4p Gβ subunit. To identify the precise function of these genes in mating, different responses to pheromone were assayed in cells that either lacked or overexpressed SSF gene products. Cells containing null alleles of both SSF1 and SSF2 displayed the normal transcriptional induction response to pheromone but were unable to form mating projections. Overexpression of SSF1 conferred the ability to form mating projections on cells containing a temperature-sensitive STE4 allele, but had only a small effect on transcriptional induction. SSF1 overexpression preferentially increased the mating efficiency of a strain containing a null allele of SPA2, a gene that functions specifically in cell morphology. To investigate whether Ssf1p plays a direct physical role in mating projection formation, its subcellular location was determined. An Ssf1p-GFP fusion was found to localize to the nucleolus, implying that the role of SSF gene products in projection formation is indirect. The region of Ssf1p-GFP localization in cells undergoing projection formation was larger and more diffuse, and was often present in a specific orientation with respect to the projection. Although the function of Ssf1p appears to originate in the nucleus, it is likely that it ultimately acts on one or more of the proteins that is directly involved in the morphological response to pheromone. Because many of the proteins required for projection formation during mating are also required for bud formation during vegetative growth, regulation of the activity or amount of one or more of these proteins by Ssf1p could explain its role in both mating and dividing cells.

scholarly journals Evidence for Related Functions of the RNA Genes of Saccharomyces cerevisiae

Genetics ◽  
1987 ◽  
Vol 117 (4) ◽  
pp. 619-631
Author(s):  
Robert L Last ◽  
Janine R Maddock ◽  
John L Woolford
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gene Function ◽  
Copy Number ◽  
Null Alleles ◽  
Yeast Genome ◽  
Temperature Sensitive ◽  
Gene Products ◽  
Nuclear Intron ◽  
Yeast Genes ◽  
Rna Genes

ABSTRACT The yeast genes RNA2-RNA11 are necessary for splicing of nuclear intron-containing pre-mRNAs. We investigated the relationships among these genes by asking whether increased expression of one RNA gene leads to suppression of the temperature-sensitive lethality of a mutation in any other RNA gene. The presence of extra plasmid-borne copies of the RNA3 gene relieves the lethality of temperature-sensitive rna4 mutations. A region of the yeast genome (SRN2) is described that suppresses temperature-sensitive rna2 mutations when it is present on either medium or high-copy number plasmids. Neither suppression occurs via a bypass of RNA gene function since null alleles of rna2 and rna4 are not suppressed by elevated dosage of SRN2 and RNA3, respectively. These results suggest that the SRN2 and RNA2 gene products have related functions, as do the RNA3 and RNA4 gene products.

scholarly journals A novel suppressor of ras1 in fission yeast, byr4, is a dosage-dependent inhibitor of cytokinesis.

1996 ◽  
Vol 133 (6) ◽  
pp. 1307-1319 ◽  
Author(s):  
K Song ◽  
K E Mach ◽  
C Y Chen ◽  
T Reynolds ◽  
C F Albright
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Mitotic Cell ◽  
Genetic Interactions ◽  
Null Alleles ◽  
Gene Products ◽  
Actin Ring ◽  
Cycle Progression ◽  
Cycle Arrest ◽  
In Cells

A novel gene, designated byr4, was identified in Schizosaccharomyces pombe that affects the mitotic cell cycle and shows genetic interactions with the ras1 signaling pathways. Null alleles of byr4 cause cell cycle arrest in late mitosis and permit multiple rounds of septation. The multiple septa typically divide two nuclei, but the nuclei frequently do not stain equally with 4',6-diamidino-2-phenylindole (DAPI), suggesting that byr4 is required for proper karyokinesis. Overexpression of byr4 inhibits cytokinesis, but cell cycle progression continues leading to multinucleate cells. When byr4 is overexpressed, the early steps in the cytokinesis pathway, including formation of the medial F-actin ring, occur normally; however, the later steps in the pathway, including contraction of the F-actin ring, septation, and rearrangement of the medial F-actin following mitosis, rarely occur, byr4 shows two genetic interactions with ras1. The inhibition of cytokinesis by byr4 overexpression was exacerbated by null alleles of ras1 and scd1, suggesting a link between pathways needed for cell polarity and cytokinesis. Overexpression of byr4 also partially bypasses the need for ras1 for sporulation. The electrophoretic mobility of the byr4 protein varied in response to mutants that perturb cytokinesis and karyokinesis, suggesting interactions between byr4 and these gene products. A more rapidly migrating byr4 protein was found in cells with mutations in cdc16, which undergo repeated septation, and in cdc15, which fail to form a medial F-actin ring in mitosis. A slower migrating byr4 protein was found in cells with a mutation in the beta-tubulin gene, which arrests cells at the metaphase-anaphase transition.

scholarly journals Identification and Characterization of Genes That Interact With lin-12 in Caenorhabditis elegans

Genetics ◽  
1997 ◽  
Vol 147 (4) ◽  
pp. 1675-1695 ◽  
Author(s):  
Frans E Tax ◽  
James H Thomas ◽  
Edwin L Ferguson ◽  
H Robert Horvitzt
Keyword(s):  
Cell Fate ◽  
Low Frequency ◽  
Signal Transduction Pathway ◽  
Temperature Shift ◽  
Egg Laying ◽  
Null Alleles ◽  
Temperature Sensitive ◽  
Loss Of Function ◽  
Gain Of Function ◽  
Suppressor Mutations

Abstract We identified and characterized 14 extragenic mutations that suppressed the dominant egg-laying defect of certain lin-12 gain-of-function mutations. These suppressors defined seven genes: sup-l7, lag-2, sel-4, sel-5, sel-6, sel-7 and sel-8. Mutations in six of the genes are recessive suppressors, whereas the two mutations that define the seventh gene, lag-2, are semi-dominant suppressors. These suppressor mutations were able to suppress other lin-12 gain-of-function mutations. The suppressor mutations arose at a very low frequency per gene, 10-50 times below the typical loss-of-function mutation frequency. The suppressor mutations in sup1 7 and lag-2 were shown to be rare non-null alleles, and we present evidence that null mutations in these two genes cause lethality. Temperature-shift studies for two suppressor genes, sup1 7and lag-2, suggest that both genes act at approximately the same time as lin-12in specifying a cell fate. Suppressor alleles of six of these genes enhanced a temperature-sensitive loss-of-function allele of glp-1, a gene related to lin-12 in structure and function. Our analysis of these suppressors suggests that the majority of these genes are part of a shared lin-12/glp-1 signal transduction pathway, or act to regulate the expression or stability of lin-12 and glp-1.

scholarly journals Export from Pericentriolar Endocytic Recycling Compartment to Cell Surface Depends on Stable, Detyrosinated (Glu) Microtubules and Kinesin

2002 ◽  
Vol 13 (1) ◽  
pp. 96-109 ◽  
Author(s):  
Sharron X. Lin ◽  
Gregg G. Gundersen ◽  
Frederick R. Maxfield
Keyword(s):  
Elevated Temperature ◽  
Cell Surface ◽  
Chinese Hamster Ovary ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Ovary Cell ◽  
Temperature Sensitive ◽  
Microtubule Organizing Center ◽  
Endocytic Recycling ◽  
In Cells

A significant fraction of internalized transferrin (Tf) concentrates in the endocytic recycling compartment (ERC), which is near the microtubule-organizing center in many cell types. Tf then recycles back to the cell surface. The mechanisms controlling the localization, morphology, and function of the ERC are not fully understood. We examined the relationship of Tf trafficking with microtubules (MTs), specifically the subset of stable, detyrosinated Glu MTs. We found some correlation between the level of stable Glu MTs and the distribution of the ERC; in cells with low levels of Glu MTs concentrated near to the centriole, the ERC was often tightly clustered, whereas in cells with higher levels of Glu MTs throughout the cell, the ERC was more dispersed. The clustered ERC in Chinese hamster ovary cells became dispersed when the level of Glu MTs was increased with taxol treatment. Furthermore, in a temperature-sensitive Chinese hamster ovary cell line (B104-5), the cells had more Glu MTs when the ERC became dispersed at elevated temperature. Microinjecting purified anti-Glu tubulin antibody into B104-5 cells at elevated temperature induced the redistribution of the ERC to a tight cluster. Microinjection of anti-Glu tubulin antibody slowed recycling of Tf to the cell surface without affecting Tf internalization or delivery to the ERC. Similar inhibition of Tf recycling was caused by microinjecting anti-kinesin antibody. These results suggest that stable Glu MTs and kinesin play a role in the organization of the ERC and in facilitating movement of vesicles from the ERC to the cell surface.

scholarly journals SEN1, a positive effector of tRNA-splicing endonuclease in Saccharomyces cerevisiae.

1992 ◽  
Vol 12 (5) ◽  
pp. 2154-2164 ◽  
Author(s):  
D J DeMarini ◽  
M Winey ◽  
D Ursic ◽  
F Webb ◽  
M R Culbertson
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Amino Acid ◽  
Gene Product ◽  
Signal Sequence ◽  
Null Alleles ◽  
Nucleoside Triphosphate ◽  
Temperature Sensitive ◽  
Yeast Saccharomyces Cerevisiae ◽  
Amino Terminal

The SEN1 gene, which is essential for growth in the yeast Saccharomyces cerevisiae, is required for endonucleolytic cleavage of introns from all 10 families of precursor tRNAs. A mutation in SEN1 conferring temperature-sensitive lethality also causes in vivo accumulation of pre-tRNAs and a deficiency of in vitro endonuclease activity. Biochemical evidence suggests that the gene product may be one of several components of a nuclear-localized splicing complex. We have cloned the SEN1 gene and characterized the SEN1 mRNA, the SEN1 gene product, the temperature-sensitive sen1-1 mutation, and three SEN1 null alleles. The SEN1 gene corresponds to a 6,336-bp open reading frame coding for a 2,112-amino-acid protein (molecular mass, 239 kDa). Using antisera directed against the C-terminal end of SEN1, we detect a protein corresponding to the predicted molecular weight of SEN1. The SEN1 protein contains a leucine zipper motif, consensus elements for nucleoside triphosphate binding, and a potential nuclear localization signal sequence. The carboxy-terminal 1,214 amino acids of the SEN1 protein are essential for growth, whereas the amino-terminal 898 amino acids are dispensable. A sequence of approximately 500 amino acids located in the essential region of SEN1 has significant similarity to the yeast UPF1 gene product, which is involved in mRNA turnover, and the mouse Mov-10 gene product, whose function is unknown. The mutation that creates the temperature-sensitive sen1-1 allele is located within this 500-amino-acid region, and it causes a substitution for an amino acid that is conserved in all three proteins.

Induced cellular DNA synthesis by ‘early’ and ‘late’ temperature-sensitive mutants of polyoma virus

1971 ◽  
Vol 177 (1046) ◽  
pp. 59-63 ◽  
Keyword(s):  
Dna Synthesis ◽  
Polyoma Virus ◽  
Viral Gene ◽  
Temperature Sensitive ◽  
Gene Products ◽  
Virus Growth ◽  
Temperature Sensitive Mutants ◽  
Cellular Dna

Temperature-sensitive mutants of polyoma virus have been examined to determine whether they are able to induce the synthesis of cellular DNA under conditions where viral gene products are defective. Two ‘early’ mutants, and one ‘late’ mutant of polyoma induce cellular DNA synthesis normally under conditions where virus growth is inhibited because viral gene products are defective.

scholarly journals Mutations affecting the tRNA-splicing endonuclease activity of Saccharomyces cerevisiae.

Genetics ◽  
1988 ◽  
Vol 118 (4) ◽  
pp. 609-617
Author(s):  
M Winey ◽  
M R Culbertson
Keyword(s):  
Growth Defect ◽  
Temperature Sensitive ◽  
Gene Products ◽  
Endonuclease Activity ◽  
Temperature Dependent ◽  
Direct Role ◽  
Trna Splicing

Abstract Two unlinked mutations that alter the enzyme activity of tRNA-splicing endonuclease have been identified in yeast. The sen1-1 mutation, which maps on chromosome 12, causes temperature-sensitive growth, reduced in vitro endonuclease activity, and in vivo accumulation of unspliced pre-tRNAs. The sen2-1 mutation does not confer a detectable growth defect, but causes a temperature-dependent reduction of in vitro endonuclease activity. Pre-tRNAs do not accumulate in sen2-1 strains. The in vitro enzyme activities of sen1-1 and sen2-1 complement in extracts from a heterozygous diploid, but fail to complement in mixed extracts from separate sen1-1 and sen2-1 haploid strains. These results suggest a direct role for SEN gene products in the enzymatic removal of introns from tRNA that is distinct from the role of other products known to affect tRNA splicing.

scholarly journals SUPPRESSORS OF snf  2 MUTATIONS RESTORE INVERTASE DEREPRESSION AND CAUSE TEMPERATURE-SENSITIVE LETHALITY IN YEAST

Genetics ◽  
1986 ◽  
Vol 112 (4) ◽  
pp. 741-753
Author(s):  
Lenore Neigeborn ◽  
Kenneth Rubin ◽  
Marian Carlson
Keyword(s):  
Genetic Background ◽  
Glucose Deprivation ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Suppressor Mutations ◽  
Invertase Gene ◽  
Selection For ◽  
Galactose Utilization ◽  
Yeast Genes ◽  
Recessive Defect

ABSTRACT Mutations in the SNF2 gene of Saccharomyces cerevisiae prevent derepression of the SUC2 (invertase) gene, and other glucose-repressible genes, in response to glucose deprivation. We have isolated 25 partial phenotypic revertants of a snf2 mutant that are able to derepress secreted invertase. These revertants all carried suppressor mutations at a single locus, designated SSN20 (suppressor of snf2). Alleles with dominant, partially dominant and recessive suppressor phenotypes were recovered, but all were only partial suppressors of snf2, reversing the defect in invertase synthesis but not other defects. All alleles also caused recessive, temperature-sensitive lethality and a recessive defect in galactose utilization, regardless of the SNF2 genotype. No significant effect on SUC2 expression was detected in a wild-type (SNF2) genetic background. The ssn20 mutations also suppressed the defects in invertase derepression caused by snf5 and snf6 mutations, and selection for invertase-producing revertants of snf5 mutants yielded only additional ssn20 alleles. These findings suggest that the roles of the SNF2, SNF5 and SNF6 genes in regulation of SUC2 are functionally related and that SSN20 plays a role in expression of a variety of yeast genes.

A DrosophilaSNAP-25Null Mutant Reveals Context-Dependent Redundancy WithSNAP-24in Neurotransmission

Genetics ◽  
2002 ◽  
Vol 162 (1) ◽  
pp. 259-271 ◽  
Author(s):  
Ilya Vilinsky ◽  
Bryan A Stewart ◽  
James Drummond ◽  
Iain Robinson ◽  
David L Deitcher
Keyword(s):  
Synaptic Transmission ◽  
Larval Stage ◽  
Neurotransmitter Release ◽  
Synaptic Proteins ◽  
Null Alleles ◽  
Temperature Sensitive ◽  
Mutant Form ◽  
F1 Progeny ◽  
Sensitive Allele ◽  
Pharate Adult

AbstractThe synaptic protein SNAP-25 is an important component of the neurotransmitter release machinery, although its precise function is still unknown. Genetic analysis of other synaptic proteins has yielded valuable information on their role in synaptic transmission. In this study, we performed a mutagenesis screen to identify new SNAP-25 alleles that fail to complement our previously isolated recessive temperature-sensitive allele of SNAP-25, SNAP-25ts. In a screen of 100,000 flies, 26 F1 progeny failed to complement SNAP-25ts and 21 of these were found to be null alleles of SNAP-25. These null alleles die at the pharate adult stage and electroretinogram recordings of these animals reveal that synaptic transmission is blocked. At the third instar larval stage, SNAP-25 nulls exhibit nearly normal neurotransmitter release at the neuromuscular junction. This is surprising since SNAP-25ts larvae exhibit a much stronger synaptic phenotype. Our evidence indicates that a related protein, SNAP-24, can substitute for SNAP-25 at the larval stage in SNAP-25 nulls. However, if a wild-type or mutant form of SNAP-25 is present, then SNAP-24 does not appear to take part in neurotransmitter release at the larval NMJ. These results suggest that the apparent redundancy between SNAP-25 and SNAP-24 is due to inappropriate genetic substitution.

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