scholarly journals Ty1 Mobilizes Subtelomeric Y′ Elements in Telomerase-Negative Saccharomyces cerevisiae Survivors

2004 ◽  
Vol 24 (22) ◽  
pp. 9887-9898 ◽  
Author(s):  
Patrick H. Maxwell ◽  
Candice Coombes ◽  
Alison E. Kenny ◽  
Joseph F. Lawler ◽  
Jef D. Boeke ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transcription Factor ◽  
Cell Division ◽  
Long Terminal Repeat ◽  
Reverse Transcription ◽  
Telomere Maintenance ◽  
Nonpermissive Temperature ◽  
Telomeric Dna ◽  
Copy Numbers ◽  
Ty1 Retrotransposition

ABSTRACT When telomerase is inactivated in Saccharomyces cerevisiae, telomeric DNA shortens with every cell division, and cells stop dividing after ∼100 generations. Survivors that form in these senescent populations and resume growing have variably amplified arrays of subtelomeric Y′ elements. We marked a chromosomal Y′ element with the his3AI retrotransposition indicator gene and found that Y′HIS3 cDNA was incorporated into the genome at ∼10- to 1,000-fold-higher frequencies in survivors compared to telomerase-positive strains. Y′HIS3 cDNA mobility was significantly reduced if assayed at 30°C, a nonpermissive temperature for Ty1 retrotransposition, or in the absence of Tec1p, a transcription factor for Ty1. Microarray analysis revealed that Y′ RNA is preferentially associated with Ty1 virus-like particles (VLPs). Genomic copies of Y′HIS3 cDNA typically have downstream oligo(A) tracts, followed by a complete Ty1 long terminal repeat and TYA1 or TYB1 sequences. These data are consistent with the use of Ty1 cDNA to prime reverse transcription of polyadenylated Y′ RNA within Ty1 VLPs. Unmarked Y′-oligo(A)-Ty1 cDNA was also detected in survivors, reaching copy numbers of ∼10−2 per genome. We propose that Y′-oligo(A)-Ty1 cDNA recombines with Y′ elements at eroding telomeres in survivors and may play a role in telomere maintenance in the absence of telomerase.

Posttranslational Inhibition of Ty1 Retrotransposition by Nucleotide Excision Repair/Transcription Factor TFIIH Subunits Ssl2p and Rad3p

Genetics ◽  
1998 ◽  
Vol 148 (4) ◽  
pp. 1743-1761
Author(s):  
Bum-Soo Lee ◽  
Conrad P Lichtenstein ◽  
Brenda Faiola ◽  
Lori A Rinckel ◽  
William Wysock ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transcription Factor ◽  
Nucleotide Excision Repair ◽  
Reverse Transcription ◽  
Excision Repair ◽  
Dna Helicase ◽  
Site Preferences ◽  
Nucleotide Excision ◽  
Ty1 Retrotransposition ◽  
High Level

Abstract rtt4-1 (regulator of Ty transposition) is a cellular mutation that permits a high level of spontaneous Ty1 retrotransposition in Saccharomyces cerevisiae. The RTT4 gene is allelic with SSL2 (RAD25), which encodes a DNA helicase present in basal transcription (TFIIH) and nucleotide excision repair (NER) complexes. The ssl2-rtt (rtt4-1) mutation stimulates Ty1 retrotransposition, but does not alter Ty1 target site preferences, or increase cDNA or mitotic recombination. In addition to ssl2-rtt, the ssl2-dead and SSL2-1 mutations stimulate Ty1 transposition without altering the level of Ty1 RNA or proteins. However, the level of Ty1 cDNA markedly increases in the ssl2 mutants. Like SSL2, certain mutations in another NER/TFIIH DNA helicase encoded by RAD3 stimulate Ty1 transposition. Although Ssl2p and Rad3p are required for NER, inhibition of Ty1 transposition is independent of Ssl2p and Rad3p NER functions. Our work suggests that NER/TFIIH subunits antagonize Ty1 transposition posttranslationally by inhibiting reverse transcription or destabilizing Ty1 cDNA.

Characterization of two telomeric DNA processing reactions in Saccharomyces cerevisiae

1988 ◽  
Vol 8 (11) ◽  
pp. 4642-4650
Author(s):  
A W Murray ◽  
T E Claus ◽  
J W Szostak
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Division ◽  
Dna Polymerase ◽  
Dna Sequences ◽  
Inverted Repeat ◽  
Telomeric Sequence ◽  
Telomeric Dna ◽  
Telomeric Sequences ◽  
Telomere Elongation

We have investigated two reactions that occur on telomeric sequences introduced into Saccharomyces cerevisiae cells by transformation. The elongation reaction added repeats of the yeast telomeric sequence C1-3A to telomeric sequences at the end of linear DNA molecules. The reaction worked on the Tetrahymena telomeric sequence C4A2 and also on the simple repeat CA. The reaction was orientation specific: it occurred only when the GT-rich strand ran 5' to 3' towards the end of the molecule. Telomere elongation occurred by non-template-directed DNA synthesis rather than any type of recombination with chromosomal telomeres, because C1-3A repeats could be added to unrelated DNA sequences between the CA-rich repeats and the terminus of the transforming DNA. The elongation reaction was very efficient, and we believe that it was responsible for maintaining an average telomere length despite incomplete replication by template-directed DNA polymerase. The resolution reaction processed a head-to-head inverted repeat of telomeric sequences into two new telomeres at a frequency of 10(-2) per cell division.

scholarly journals Characterization of two telomeric DNA processing reactions in Saccharomyces cerevisiae.

1988 ◽  
Vol 8 (11) ◽  
pp. 4642-4650 ◽  
Author(s):  
A W Murray ◽  
T E Claus ◽  
J W Szostak
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Division ◽  
Dna Polymerase ◽  
Dna Sequences ◽  
Inverted Repeat ◽  
Telomeric Sequence ◽  
Telomeric Dna ◽  
Telomeric Sequences ◽  
Telomere Elongation

We have investigated two reactions that occur on telomeric sequences introduced into Saccharomyces cerevisiae cells by transformation. The elongation reaction added repeats of the yeast telomeric sequence C1-3A to telomeric sequences at the end of linear DNA molecules. The reaction worked on the Tetrahymena telomeric sequence C4A2 and also on the simple repeat CA. The reaction was orientation specific: it occurred only when the GT-rich strand ran 5' to 3' towards the end of the molecule. Telomere elongation occurred by non-template-directed DNA synthesis rather than any type of recombination with chromosomal telomeres, because C1-3A repeats could be added to unrelated DNA sequences between the CA-rich repeats and the terminus of the transforming DNA. The elongation reaction was very efficient, and we believe that it was responsible for maintaining an average telomere length despite incomplete replication by template-directed DNA polymerase. The resolution reaction processed a head-to-head inverted repeat of telomeric sequences into two new telomeres at a frequency of 10(-2) per cell division.

scholarly journals Suppression of cdc13-2-associated senescence by pif1-m2 requires Ku-mediated telomerase recruitment

2021 ◽  
Author(s):  
Enikő Fekete-Szücs ◽  
Fernando Rodrigo Rosas Bringas ◽  
Sonia Stinus ◽  
Michael Chang
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Replicative Senescence ◽  
Telomere Maintenance ◽  
Telomerase Rna ◽  
Telomeric Dna ◽  
Insight Into

In Saccharomyces cerevisiae, recruitment of telomerase to telomeres requires an interaction between Cdc13, which binds single-stranded telomeric DNA, and the Est1 subunit of telomerase. A second pathway involving an interaction between the yKu complex and telomerase RNA (TLC1) contributes to telomerase recruitment, but cannot sufficiently recruit telomerase on its own to prevent replicative senescence when the primary Cdc13-Est1 pathway is abolished—for example, in the cdc13-2 mutant. In this study, we find that mutation of PIF1, which encodes a helicase that inhibits telomerase, suppresses the replicative senescence of cdc13-2 by increasing reliance on the yKu-TLC1 pathway for telomerase recruitment. Our findings reveal new insight into telomerase-mediated telomere maintenance.

scholarly journals Retrotransposon Suicide: Formation of Ty1 Circles and Autointegration via a Central DNA Flap

2006 ◽  
Vol 80 (24) ◽  
pp. 11920-11934 ◽  
Author(s):  
David J. Garfinkel ◽  
Karen M. Stefanisko ◽  
Katherine M. Nyswaner ◽  
Sharon P. Moore ◽  
Jangsuk Oh ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Homologous Recombination ◽  
Dna Synthesis ◽  
Long Terminal Repeat ◽  
Reverse Transcription ◽  
Copy Number ◽  
Retroviral Infection ◽  
Dna Structures ◽  
Dead End ◽  
Central Polypurine Tract

ABSTRACT Despite their evolutionary distance, the Saccharomyces cerevisiae retrotransposon Ty1 and retroviruses use similar strategies for replication, integration, and interactions with their hosts. Here we examine the formation of circular Ty1 DNA, which is comparable to the dead-end circular products that arise during retroviral infection. Appreciable levels of circular Ty1 DNA are present with one-long terminal repeat (LTR) circles and deleted circles comprising major classes, while two-LTR circles are enriched when integration is defective. One-LTR circles persist when homologous recombination pathways are blocked by mutation, suggesting that they result from reverse transcription. Ty1 autointegration events readily occur, and many are coincident with and dependent upon DNA flap structures that result from DNA synthesis initiated at the central polypurine tract. These results suggest that Ty1-specific mechanisms minimize copy number and raise the possibility that special DNA structures are a targeting determinant.

scholarly journals Nsr1, a nitrogen source-regulated microprotein, confers an alternative mechanism of G1/S transcriptional activation in budding yeast

2020 ◽  
Author(s):  
Sylvain Tollis ◽  
Jaspal Singh ◽  
Yogitha Thattikota ◽  
Xiaojing Tang ◽  
Susan Moore ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Transcription Factor ◽  
Cell Division ◽  
Nutrient Availability ◽  
Budding Yeast ◽  
Transcriptional Activator ◽  
Transcription Factor Complex ◽  
Commitment To Cell Division ◽  
Nutrient Conditions

AbstractCommitment to cell division at the end of G1 phase, termed Start in the budding yeast Saccharomyces cerevisiae, is strongly influenced by nutrient availability. To identify new dominant activators of Start that might operate under different nutrient conditions, we screened a genome-wide ORF overexpression library for genes that bypass a Start arrest caused by absence of the G1 cyclin Cln3 and the transcriptional activator Bck2. We recovered a hypothetical gene YLR053c, renamed NSR1 for Nitrogen-responsive Start Regulator 1, which encodes a poorly characterized 108 amino acid microprotein. Endogenous Nsr1 was nuclear-localized, restricted to poor nitrogen conditions, induced upon mTORC1 inhibition, and cell cycle-regulated with a peak at Start. NSR1 interacted genetically with SWI4 and SWI6, which encode the master G1/S transcription factor complex SBF. Correspondingly, Nsr1 physically interacted with Swi4 and Swi6 and was localized to G1/S promoter DNA. Nsr1 exhibited inherent transactivation activity and fusion of Nsr1 to the SBF inhibitor Whi5 was sufficient to suppress other Start defects. Nsr1 appears to be a recently evolved microprotein that rewires the G1/S transcriptional machinery under poor nutrient conditions.Author SummaryUnicellular microorganisms must adapt to ever-changing nutrient conditions and hence must adjust cell growth and proliferation to maximize fitness. In the budding yeast Saccharomyces cerevisiae, commitment to cell division, termed Start, is heavily influenced by nutrient availability. The mechanisms of Start activation under conditions of nutrient limitation are less well characterized than under nutrient excess. To identify potential new Start regulators specific to poor nutrient environments, we screened for genes able to bypass a genetic Start arrest caused by loss of the G1 cyclin Cln3 and the transcriptional activator Bck2. This screen uncovered YLR053c, which we renamed NSR1 for Nitrogen-responsive Start Regulator. Sequence analysis across yeast species indicated that Nsr1 is a recently-evolved microprotein. We showed that NSR1 is nutrient- and cell cycle-regulated, and directly binds the main G1/S transcription factor complex SBF. We demonstrated that Nsr1 has an intrinsic trans-activation activity and provided genetic evidence to suggest that Nsr1 can bypass the requirement for normal Cln3-dependent activation of SBF. These results uncover a new mechanism of Start activation and demonstrate how microproteins can rapidly emerge to rewire fundamental cellular processes.

scholarly journals Posttranslational interference of Ty1 retrotransposition by antisense RNAs

2009 ◽  
Vol 106 (37) ◽  
pp. 15657-15662 ◽  
Author(s):  
Emiko Matsuda ◽  
David J. Garfinkel
Keyword(s):  
Gene Expression ◽  
Saccharomyces Cerevisiae ◽  
Rna Interference ◽  
Transposable Elements ◽  
Reverse Transcription ◽  
Copy Number ◽  
Dramatic Decrease ◽  
Intrinsic Mechanism ◽  
In Trans ◽  
Ty1 Retrotransposition

Transposable elements impact genome function by altering gene expression and causing chromosome rearrangements. As a result, organisms have evolved mechanisms, such as RNA-interference, to minimize the level of transposition. However, organisms without the conserved RNAi pathways, likeSaccharomyces cerevisiae, must use other mechanisms to prevent transposon movement. Here, we provide evidence that antisense (AS) RNAs from the retrovirus-like element Ty1 inhibit retrotransposition posttranslationally inSaccharomyces. Multiple Ty1AS transcripts overlap Ty1 sequences necessary for copy number control (CNC) and inhibit transpositionin trans. Altering Ty1 copy number or deleting sequences in the CNC region that are required for reverse transcription affect Ty1AS RNA level and Ty1 movement. Ty1AS RNAs are enriched in virus-like particles, and are associated with a dramatic decrease in the level of integrase, less reverse transcriptase, and an inability to synthesize Ty1 cDNA. Thus, Ty1AS RNAs are part of an intrinsic mechanism that limits retrotransposition by reducing the level of proteins required for replication and integration.

scholarly journals Suppression of cdc13-2-associated senescence by pif1-m2 requires Ku-mediated telomerase recruitment

2021 ◽  
Author(s):  
Enikő Fekete-Szücs ◽  
Fernando R Rosas Bringas ◽  
Sonia Stinus ◽  
Michael Chang
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Replicative Senescence ◽  
Telomere Maintenance ◽  
Telomerase Rna ◽  
Telomeric Dna ◽  
Insight Into

Abstract In Saccharomyces cerevisiae, recruitment of telomerase to telomeres requires an interaction between Cdc13, which binds single-stranded telomeric DNA, and the Est1 subunit of telomerase. A second pathway involving an interaction between the yKu complex and telomerase RNA (TLC1) contributes to telomerase recruitment, but cannot sufficiently recruit telomerase on its own to prevent replicative senescence when the primary Cdc13-Est1 pathway is abolished—for example, in the cdc13-2 mutant. In this study, we find that mutation of PIF1, which encodes a helicase that inhibits telomerase, suppresses the replicative senescence of cdc13-2 by increasing reliance on the yKu-TLC1 pathway for telomerase recruitment. Our findings reveal new insight into telomerase-mediated telomere maintenance.

scholarly journals Extrachromosomal Telomeric Circles Contribute to Rad52-, Rad50-, and Polymerase δ-Mediated Telomere-Telomere Recombination in Saccharomyces cerevisiae

2005 ◽  
Vol 4 (2) ◽  
pp. 327-336 ◽  
Author(s):  
Chi-Ying Lin ◽  
Hsih-Hsuan Chang ◽  
Kou-Juey Wu ◽  
Shun-Fu Tseng ◽  
Chuan-Chuan Lin ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Reverse Transcriptase ◽  
Telomere Maintenance ◽  
Yeast Cells ◽  
Chromosome Stability ◽  
Telomerase Reverse Transcriptase ◽  
Wild Type ◽  
Telomeric Dna ◽  
Recombination Mechanism

ABSTRACT Telomere maintenance is required for chromosome stability, and telomeres are typically replicated by the telomerase reverse transcriptase. In both tumor and yeast cells that lack telomerase, telomeres are maintained by an alternative recombination mechanism. By using an in vivo inducible Cre-loxP system to generate and trace the fate of marked telomeric DNA-containing rings, the efficiency of telomere-telomere recombination can be determined quantitatively. We show that the telomeric loci are the primary sites at which a marked telomeric ring-containing DNA is observed among wild-type and surviving cells lacking telomerase. Marked telomeric DNAs can be transferred to telomeres and form tandem arrays through Rad52-, Rad50-, and polymerase δ-mediated recombination. Moreover, increases of extrachromosomal telomeric and Y′ rings were observed in telomerase-deficient cells. These results imply that telomeres can use looped-out telomeric rings to promote telomere-telomere recombination in telomerase-deficient Saccharomyces cerevisiae.

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