Ty1 and Ty5 of<i>Saccharomyces cerevisiae</i>

Voytas, Daniel F.; Boeke, Jef D.

doi:10.1128/9781555817954.ch26

Cited by 86 publications

(80 citation statements)

References 216 publications

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“…On the top is a scheme for Ty1 Gag processing. Most Gag-p45 protein is derived from PR-mediated cleavage of the Gag-p49 precursor near the C terminus (reviewed by Voytas and Boeke 2002). A minor amount of Gag-p45 is derived by cleavage of the Gag-Pol-p199 precursor protein Kawakami et al 1993) that is produced by 11 frameshifting (11Fs).…”

Section: Resultsmentioning

confidence: 99%

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BUD22 Affects Ty1 Retrotransposition and Ribosome Biogenesis in Saccharomyces cerevisiae

et al. 2010

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A variety of cellular factors affect the movement of the retrovirus-like transposon Ty1. To identify genes involved in Ty1 virus-like particle (VLP) function, the level of the major capsid protein (Gag-p45) and its proteolytic precursor (Gag-p49p) was monitored in a subset of Ty1 cofactor mutants. Twenty-nine of 87 mutants contained alterations in the level of Gag; however, only bud22D showed a striking defect in Gag processing. BUD22 affected the 11 translational frameshifting event required to express the Pol proteins protease, integrase, and reverse transcriptase. Therefore, it is possible that the bud22D mutant may not produce enough functional Ty1 protease to completely process Gag-p49 to p45. Furthermore, BUD22 is required for 18S rRNA processing and 40S subunit biogenesis and influences polysome density. Together our results suggest that BUD22 is involved in a step in ribosome biogenesis that not only affects general translation, but also may alter the frameshifting efficiency of ribosomes, an event central to Ty1 retrotransposition.

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Section: Resultsmentioning

confidence: 99%

“…structurally and functionally related to retroviruses (Voytas and Boeke 2002). Ty1 elements are flanked by long terminal repeats (LTRs) and are transcribed from end to end, resulting in an mRNA that serves as a template for both translation and reverse transcription.…”

Section: T He Saccharomyces Cerevisiae Retrotransposon Ty1 Ismentioning

confidence: 99%

BUD22 Affects Ty1 Retrotransposition and Ribosome Biogenesis in Saccharomyces cerevisiae

et al. 2010

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“…Ty1 RNA is one of the most abundant mRNA species in yeast, but only one copy of Ty1 cDNA is present for every 10,000 Ty1 transcripts, and transposition is rare (reviewed in ref. 2). Over 30 host factors that inhibit retrotransposition have been identified (3)(4)(5)(6)(7).…”

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confidence: 99%

Activation of a LTR-retrotransposon by telomere erosion

Scholes

Kenny

Gamache

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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Retrotransposons can facilitate repair of broken chromosomes, and therefore an important question is whether the host can activate retrotransposons in response to chromosomal lesions. Here we show that Ty1 elements, which are LTR-retrotransposons in Saccharomyces cerevisiae, are mobilized when DNA lesions are created by the loss of telomere function. Inactivation of telomerase in yeast results in progressive shortening of telomeric DNA, eventually triggering a DNA-damage checkpoint that arrests cells in G 2͞M. A fraction of cells, termed survivors, recover from arrest by forming alternative telomere structures. When telomerase is inactivated, Ty1 retrotransposition increases substantially in parallel with telomere erosion and then partially declines when survivors emerge. Retrotransposition is stimulated at the level of Ty1 cDNA synthesis, causing cDNA levels to increase 20-fold or more before survivors form. This response is elicited through a signaling pathway that includes Rad24, Rad17, and Rad9, three components of the DNAdamage checkpoint. Our findings indicate that Ty1 retrotransposons are activated as part of the cellular response to telomere dysfunction.

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“…Pol is made as a Gag-Pol read-through protein by translational frameshifting (Belcourt and Farabaugh 1990). Gag and Gag-Pol proteins are coassembled with Ty1 RNA and the yeast initiator tRNA iMet within the cytoplasm, forming virus-like particles (VLPs) (Chapman et al 1992;Roth 2000;Voytas and Boeke 2002). VLPs are direct transposition intermediates in which reverse transcription occurs Eichinger and Boeke 1988).…”

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confidence: 99%

Identification and characterization of critical cis-acting sequences within the yeast Ty1 retrotransposon

Bolton

Coombes

Eby

et al. 2005

RNA

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The yeast long terminal repeat (LTR) retrotransposon Ty1, like retroviruses, encodes a terminally redundant RNA, which is packaged into virus-like particles (VLPs) and is converted to a DNA copy by the process of reverse transcription. Mutations predicted to interfere with the priming events during reverse transcription and hence inhibit replication are known to dramatically decrease transposition of Ty1. However, additional cis-acting sequences responsible for Ty1 replication and RNA dimerization and packaging have remained elusive. Here we describe a modular mini-Ty1 element encoding the minimal sequence that can be retrotransposed by the Ty1 proteins, supplied in trans by a helper construct. Using a mutagenic screening strategy, we recovered transposition-deficient modular mini-Ty1-HIS3 elements with mutations in sequences required in cis for Ty1 replication and integration. Two distinct clusters of mutations mapped near the 5-end of the Ty1 RNA. The clusters define a GAGGAGA sequence at the extreme 5-end of the Ty1 transcript and a complementary downstream UCUCCUC sequence, 264 nt into the RNA. Disruption of the reverse complementarity of these two sequences decreased transposition and restoration of complementarity rescued transposition to wild-type levels. Ty1 cDNA was reduced in cells expressing RNAs with mutations in either of these short sequences, despite nearly normal levels of Ty1 RNA and VLPs. Our results suggest that the intramolecular interaction between the 5-GAGGAGA and UCUCCUC sequences stabilizes an RNA structure required for efficient initiation of reverse transcription. Keywords: RNA; intramolecular interaction; mutagenesisTy1 is one of five types of long terminal repeat (LTR) retrotransposons inhabiting the genome of the yeast Saccharomyces cerevisiae. LTR retrotransposons, such as Ty1, are similar to retroviruses in many aspects (Boeke and Stoye 1997;Voytas and Boeke 2002). Analogous to retroviruses, Ty1 elements consist of a central coding region flanked by directly repeated LTRs, which are divided into the U3, R, and U5 regions. The Ty1 lifecycle, a streamlined version of the retroviral lifecycle, can be divided into three phases: (1) expression and assembly, (2) reverse transcription, and (3) integration. Transcription of Ty1 produces a terminally redundant RNA molecule, which serves dual functions. First, translation of the element-encoded RNA generates the structural protein Gag and enzyme Pol, which are required for transposition, specifically for replication and integration of Ty1. Pol is made as a Gag-Pol read-through protein by translational frameshifting (Belcourt and Farabaugh 1990). Gag and Gag-Pol proteins are coassembled with Ty1 RNA and the yeast initiator tRNA iMet within the cytoplasm, forming virus-like particles (VLPs) (Chapman et al. 1992;Roth 2000;Voytas and Boeke 2002). VLPs are direct transposition intermediates in which reverse transcription occurs Eichinger and Boeke 1988). Second, during Ty1 replication, as in retroviruses, the terminally redundant RNA, th...

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Ty1 and Ty5 ofSaccharomyces cerevisiae

Cited by 86 publications

References 216 publications

BUD22 Affects Ty1 Retrotransposition and Ribosome Biogenesis in Saccharomyces cerevisiae

BUD22 Affects Ty1 Retrotransposition and Ribosome Biogenesis in Saccharomyces cerevisiae

Activation of a LTR-retrotransposon by telomere erosion

Identification and characterization of critical cis-acting sequences within the yeast Ty1 retrotransposon

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