scholarly journals Loss of Ku’s DNA end binding activity affects telomere length via destabilizing telomere-bound Est1 rather than altering TLC1 homeostasis

2019 ◽  
Author(s):  
Laramie D. Lemon ◽  
Danna K. Morris ◽  
Alison A. Bertuch
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Telomere Length ◽  
Nuclear Localization ◽  
Binding Activity ◽  
Nuclear Retention ◽  
Regulatory Subunits ◽  
Mutant Strains ◽  
Telomere Association ◽  
Telomere Length Homeostasis

ABSTRACTSaccharomyces cerevisiae telomerase, which maintains telomere length, is comprised of an RNA component, TLC1, the reverse transcriptase, Est2, and regulatory subunits, including Est1. The Yku70/Yku80 (Ku) heterodimer, a DNA end binding (DEB) protein, also contributes to telomere length maintenance. Ku binds TLC1 and telomere ends in a mutually exclusive fashion, and is required to maintain levels and nuclear localization of TLC1. Ku also interacts with Sir4, which localizes to telomeres. Here we sought to determine the role of Ku’s DEB activity in telomere length maintenance by utilizing yku70-R456E mutant strains, in which Ku has reduced DEB and telomere association but proficiency in TLC1 and Sir4 binding, and TLC1 nuclear retention. Telomere lengths in a yku70-R456E strain were nearly as short as those in ykuΔ strains and shorter than in strains lacking either Sir4, Ku:Sir4 interaction, or Ku:TLC1 interaction. TLC1 levels were decreased in the yku70-R456E mutant, yet overexpression of TLC1 failed to restore telomere length. Reduced DEB activity did not impact Est1’s ability to associate with telomerase but did result in decreased association of Est1 with the telomere. These findings suggest Ku’s DEB activity maintains telomere length homeostasis by preserving Est1’s interaction at the telomere rather than altering TLC1 levels.

scholarly journals Interactions of TLC1 (Which Encodes the RNA Subunit of Telomerase), TEL1, and MEC1 in Regulating Telomere Length in the Yeast Saccharomyces cerevisiae

1999 ◽  
Vol 19 (9) ◽  
pp. 6065-6075 ◽  
Author(s):  
Kim B. Ritchie ◽  
Julia C. Mallory ◽  
Thomas D. Petes
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Viability ◽  
Telomere Length ◽  
Telomere Maintenance ◽  
Yeast Saccharomyces Cerevisiae ◽  
Senescent Phenotype ◽  
Gradual Loss ◽  
Mutant Strains ◽  
Subtelomeric Repeats

ABSTRACT In the yeast Saccharomyces cerevisiae, chromosomes terminate with a repetitive sequence [poly(TG1–3)] 350 to 500 bp in length. Strains with a mutation of TEL1, a homolog of the human gene (ATM) mutated in patients with ataxia telangiectasia, have short but stable telomeric repeats. Mutations of TLC1 (encoding the RNA subunit of telomerase) result in strains that have continually shortening telomeres and a gradual loss of cell viability; survivors of senescence arise as a consequence of a Rad52p-dependent recombination events that amplify telomeric and subtelomeric repeats. We show that a mutation inMEC1 (a gene related in sequence to TEL1 andATM) reduces telomere length and that tel1 mec1double mutant strains have a senescent phenotype similar to that found in tlc1 strains. As observed in tlc1 strains, survivors of senescence in the tel1 mec1 strains occur by a Rad52p-dependent amplification of telomeric and subtelomeric repeats. In addition, we find that strains with both tel1 andtlc1 mutations have a delayed loss of cell viability compared to strains with the single tlc1 mutation. This result argues that the role of Tel1p in telomere maintenance is not solely a direct activation of telomerase.

scholarly journals Yeast Est2p Affects Telomere Length by Influencing Association of Rap1p with Telomeric Chromatin

2008 ◽  
Vol 28 (7) ◽  
pp. 2380-2390 ◽  
Author(s):  
Hong Ji ◽  
Christopher J. Adkins ◽  
Bethany R. Cartwright ◽  
Katherine L. Friedman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Telomere Length ◽  
Specific Binding ◽  
Telomerase Activity ◽  
Negative Regulator ◽  
Wild Type ◽  
Telomeric Dna ◽  
Telomere Length Homeostasis

ABSTRACT In Saccharomyces cerevisiae, the sequence-specific binding of the negative regulator Rap1p provides a mechanism to measure telomere length: as the telomere length increases, the binding of additional Rap1p inhibits telomerase activity in cis. We provide evidence that the association of Rap1p with telomeric DNA in vivo occurs in part by sequence-independent mechanisms. Specific mutations in EST2 (est2-LT) reduce the association of Rap1p with telomeric DNA in vivo. As a result, telomeres are abnormally long yet bind an amount of Rap1p equivalent to that observed at wild-type telomeres. This behavior contrasts with that of a second mutation in EST2 (est2-up34) that increases bound Rap1p as expected for a strain with long telomeres. Telomere sequences are subtly altered in est2-LT strains, but similar changes in est2-up34 telomeres suggest that sequence abnormalities are a consequence, not a cause, of overelongation. Indeed, est2-LT telomeres bind Rap1p indistinguishably from the wild type in vitro. Taken together, these results suggest that Est2p can directly or indirectly influence the binding of Rap1p to telomeric DNA, implicating telomerase in roles both upstream and downstream of Rap1p in telomere length homeostasis.

scholarly journals Biological role of the general control of amino acid biosynthesis in Saccharomyces cerevisiae.

1981 ◽  
Vol 1 (7) ◽  
pp. 584-593 ◽  
Author(s):  
P Niederberger ◽  
G Miozzari ◽  
R Hütter
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acid ◽  
Amino Acid Biosynthesis ◽  
Wild Type ◽  
General Control ◽  
Acid Biosynthesis ◽  
Mutant Strains ◽  
In The Wild ◽  
Amino Acid Imbalance

The biological role of the "general control of amino acid biosynthesis" has been investigated by analyzing growth and enzyme levels in wild-type, bradytrophic, and nonderepressing mutant strains of Saccharomyces cerevisiae. Amino acid limitation was achieved by using either bradytrophic mutations or external amino acid imbalance. In the wild-type strain noncoordinate derepression of enzymes subject to the general control has been found. Derepressing factors were in the order of 2 to 4 in bradytrophic mutant strains grown under limiting conditions and only in the order of 1.5 to 2 under the influence of external amino acid imbalance. Nonderepressing mutations led to slower growth rates under conditions of amino acid limitation, and no derepression of enzymes under the general control was observed. The amino acid pools were found to be very similar in the wild type and in nonderepressing mutant strains under all conditions tested. Our results indicate that the general control affects all branched amino acid biosynthetic pathways, namely, those of the aromatic amino acids and the aspartate family, the pathways for the basic amino acids lysine, histidine, and arginine, and also the pathways of serine and valine biosyntheses.

scholarly journals The genetic control of direct-repeat recombination in Saccharomyces: the effect of rad52 and rad1 on mitotic recombination at GAL10, a transcriptionally regulated gene.

Genetics ◽  
1989 ◽  
Vol 123 (4) ◽  
pp. 725-738 ◽  
Author(s):  
B J Thomas ◽  
R Rothstein
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Genetic Control ◽  
Plasmid Dna ◽  
Double Mutant ◽  
Direct Repeat ◽  
Single Mutant ◽  
Plasmid Loss ◽  
Mutant Strains ◽  
Recombination Pathway

Abstract We have previously shown direct-repeat recombination events leading to loss of a plasmid integrated at the GAL10 locus in Saccharomyces cerevisiae are stimulated by transcription of the region. We have examined the role of two recombination- and repair-defective mutations, rad1 and rad52, on direct repeat recombination in transcriptionally active and inactive sequences. We show that the RAD52 gene is required for transcription-stimulated recombination events leading to loss of the integrated plasmid. Similarly, Gal+ events between the duplicated repeats that retain the integrated plasmid DNA (Gal+ Ura+ replacement events) are reduced 20-fold in the rad52 mutant in sequences that are constitutively expressed. In contrast, in sequences that are not expressed, the rad52 mutation reduces plasmid loss events by only twofold and Gal+ Ura+ replacements by fourfold. We also observe an increase in disome-associated plasmid loss events in the rad52 mutant, indicative of chromosome gain. This event is not affected by expression of the region. Plasmid loss events in rad1 mutant strains are reduced only twofold in transcriptionally active sequences and are not affected in sequences that are repressed. However, the rad1 and rad52 double mutant shows a decrease in plasmid loss events greater than the sum of the decreases in the rates of this event displayed by either single mutant in both constitutive and repressed DNA, indicating a synergistic interaction between these two genes. The synergism is limited to recombination since the rad1 rad52 double mutant is no more sensitive when compared with either single mutant in its ability to survive radiation damage. Finally, the recombination pathway that remains in the double mutant is positively affected by transcription of the region.

scholarly journals mRNAs Encoding Telomerase Components and Regulators Are Controlled by UPF Genes in Saccharomyces cerevisiae

2003 ◽  
Vol 2 (1) ◽  
pp. 134-142 ◽  
Author(s):  
Jeffrey N. Dahlseid ◽  
Jodi Lew-Smith ◽  
Michael J. Lelivelt ◽  
Shinichiro Enomoto ◽  
Amanda Ford ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Telomere Length ◽  
Dna Sequences ◽  
Mrna Levels ◽  
Loss Of Function ◽  
Telomeric Silencing ◽  
Expression Of Genes ◽  
Mutant Strains ◽  
Genes Encoding

ABSTRACT Telomeres, the chromosome ends, are maintained by a balance of activities that erode and replace the terminal DNA sequences. Furthermore, telomere-proximal genes are often silenced in an epigenetic manner. In Saccharomyces cerevisiae, average telomere length and telomeric silencing are reduced by loss of function of UPF genes required in the nonsense-mediated mRNA decay (NMD) pathway. Because NMD controls the mRNA levels of several hundred wild-type genes, we tested the hypothesis that NMD affects the expression of genes important for telomere functions. In upf mutants, high-density oligonucleotide microarrays and Northern blots revealed that the levels of mRNAs were increased for genes encoding the telomerase catalytic subunit (Est2p), in vivo regulators of telomerase (Est1p, Est3p, Stn1p, and Ten1p), and proteins that affect telomeric chromatin structure (Sas2p and Orc5p). We investigated whether overexpressing these genes could mimic the telomere length and telomeric silencing phenotypes seen previously in upf mutant strains. Increased dosage of STN1, especially in combination with increased dosage of TEN1, resulted in reduced telomere length that was indistinguishable from that in upf mutants. Increased levels of STN1 together with EST2 resulted in reduced telomeric silencing like that of upf mutants. The half-life of STN1 mRNA was not altered in upf mutant strains, suggesting that an NMD-controlled transcription factor regulates the levels of STN1 mRNA. Together, these results suggest that NMD maintains the balance of gene products that control telomere length and telomeric silencing primarily by maintaining appropriate levels of STN1, TEN1, and EST2 mRNA.

Biological role of the general control of amino acid biosynthesis in Saccharomyces cerevisiae

1981 ◽  
Vol 1 (7) ◽  
pp. 584-593
Author(s):  
P Niederberger ◽  
G Miozzari ◽  
R Hütter
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acid ◽  
Amino Acid Biosynthesis ◽  
Wild Type ◽  
General Control ◽  
Acid Biosynthesis ◽  
Mutant Strains ◽  
In The Wild ◽  
Amino Acid Imbalance

The biological role of the "general control of amino acid biosynthesis" has been investigated by analyzing growth and enzyme levels in wild-type, bradytrophic, and nonderepressing mutant strains of Saccharomyces cerevisiae. Amino acid limitation was achieved by using either bradytrophic mutations or external amino acid imbalance. In the wild-type strain noncoordinate derepression of enzymes subject to the general control has been found. Derepressing factors were in the order of 2 to 4 in bradytrophic mutant strains grown under limiting conditions and only in the order of 1.5 to 2 under the influence of external amino acid imbalance. Nonderepressing mutations led to slower growth rates under conditions of amino acid limitation, and no derepression of enzymes under the general control was observed. The amino acid pools were found to be very similar in the wild type and in nonderepressing mutant strains under all conditions tested. Our results indicate that the general control affects all branched amino acid biosynthetic pathways, namely, those of the aromatic amino acids and the aspartate family, the pathways for the basic amino acids lysine, histidine, and arginine, and also the pathways of serine and valine biosyntheses.

scholarly journals Mig1 localization exhibits biphasic behavior which is controlled by both metabolic and regulatory roles of the sugar kinases

2020 ◽  
Vol 295 (6) ◽  
pp. 1489-1500
Author(s):  
Gregor W. Schmidt ◽  
Niek Welkenhuysen ◽  
Tian Ye ◽  
Marija Cvijovic ◽  
Stefan Hohmann
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Localization ◽  
Essential Role ◽  
Carbon Sources ◽  
Transcriptional Repressor ◽  
Energy Sources ◽  
Nucleocytoplasmic Shuttling

Abstract Glucose, fructose and mannose are the preferred carbon/energy sources for the yeast Saccharomyces cerevisiae. Absence of preferred energy sources activates glucose derepression, which is regulated by the kinase Snf1. Snf1 phosphorylates the transcriptional repressor Mig1, which results in its exit from the nucleus and subsequent derepression of genes. In contrast, Snf1 is inactive when preferred carbon sources are available, which leads to dephosphorylation of Mig1 and its translocation to the nucleus where Mig1 acts as a transcription repressor. Here we revisit the role of the three hexose kinases, Hxk1, Hxk2 and Glk1, in glucose de/repression. We demonstrate that all three sugar kinases initially affect Mig1 nuclear localization upon addition of glucose, fructose and mannose. This initial import of Mig1 into the nucleus was temporary; for continuous nucleocytoplasmic shuttling of Mig1, Hxk2 is required in the presence of glucose and mannose and in the presence of fructose Hxk2 or Hxk1 is required. Our data suggest that Mig1 import following exposure to preferred energy sources is controlled via two different pathways, where (1) the initial import is regulated by signals derived from metabolism and (2) continuous shuttling is regulated by the Hxk2 and Hxk1 proteins. Mig1 nucleocytoplasmic shuttling appears to be important for the maintenance of the repressed state in which Hxk1/2 seems to play an essential role.

scholarly journals LAS1 is an essential nuclear protein involved in cell morphogenesis and cell surface growth.

Genetics ◽  
1995 ◽  
Vol 141 (3) ◽  
pp. 857-871 ◽  
Author(s):  
A I Doseff ◽  
K T Arndt
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Surface ◽  
Nuclear Localization ◽  
Mother Cell ◽  
Nuclear Protein ◽  
Cell Morphogenesis ◽  
Bud Formation ◽  
New Gene ◽  
Cell Alterations

Abstract Saccharomyces cerevisiae mutations that cause a requirement for SSD1-v for viability were isolated, yielding one new gene, LAS1, and three previously identified genes, SIT4, BCK1/SLK1, and SMP3. Three of these genes, LAS1, SIT4, and BCK1/SLK1, encode proteins that have roles in bud formation or morphogenesis. LAS1 is essential and loss of LAS1 function causes the cells to arrest as 80% unbudded cells and 20% large budded cells that accumulate many vesicles at the mother-daughter neck. Overexpression of LAS1 results in extra cell surface projections in the mother cell, alterations in actin and SPA2 localization, and the accumulation of electron-dense structures along the periphery of both the mother cell and the bud. The nuclear localization of LAS1 suggests a role of LAS1 for regulating bud formation and morphogenesis via the expression of components that function directly in these processes.

scholarly journals ULTRAVIOLET-INDUCED REVERSION OF cyc1 ALLELES IN RADIATION-SENSITIVE STRAINS OF YEAST. III. rev3 MUTANT STRAINS

Genetics ◽  
1979 ◽  
Vol 92 (2) ◽  
pp. 397-408
Author(s):  
Christopher W Lawrence ◽  
Roshan B Christensen
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gene Function ◽  
Yeast Saccharomyces Cerevisiae ◽  
Frameshift Mutations ◽  
Mutant Strains ◽  
Unitary Model ◽  
Bacterial Mutagenesis

ABSTRACT The role of the REV3 gene function in UV-induced mutagensis in the yeast Saccharomyces cerevisiae has been examined by determining the reversion of 12 well-defined cycl mutations in diploid strains homozygous for the rev3—1 or rev3—3 allele. The 12 cycl alleles include one ochre, one amber, four initiation, two proline missense, and four frameshift mutations. We find that the rev3 mutations reduce the frequency of UV-induced reversion of all of the cycl alleles, though different classes of alleles respond to a different extent. These results imply that the REV3 gene function is required for the production of a wide variety of mutational events, though probably not all, and show that each of the three REV loci have different mutational phenotypes. Such diverse phenotypes are not predicted by the unitary model for bacterial mutagenesis (CAILLET-FAUQUET, DEFAIS and RADMAN 1977; WITKIN 1976), suggesting that this is at best an incomplete description of eukaryotic mutagenesis.

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