Happy together: the life and times of Ty retrotransposons and their hostsLesage P. · Todeschini A.L.
Institut de Biologie Physico-Chimique, CNRS UPR 9073, Paris (France)
The aim of this review is to describe the level of intimacy between Ty retrotransposons (Ty1–Ty5) and their host the yeast Saccharomyces cerevisiae. The effects of Ty location in the genome and of host proteins on the expression and mobility of Ty elements are highlighted. After a brief overview of Ty diversity and evolution, we describe the factors that dictate Ty target-site preference and the impact of targeting on Ty and adjacent gene expression. Studies on Ty3 and Ty5 have been especially informative in unraveling the role of host factors (Pol III machinery and silencing proteins, respectively) and integrase in controlling the specificity of integration. In contrast, not much is known regarding Ty1, Ty2 and Ty4, except that their insertion depends on the transcriptional competence of the adjacent Pol III gene and might be influenced by some chromatin components. This review also brings together recent findings on the regulation of Ty1 retrotransposition. A large number of host proteins (over 30) involved in a wide range of cellular processes controls either directly or indirectly Ty1 mobility, primarily at post-transcriptional steps. We focus on several genes for which more detailed analyses have permitted the elaboration of regulatory models. In addition, this review describes new data revealing that repression of Ty1 mobility also involves two forms of copy number control that act at both the trancriptional and post-transcriptional levels. Since S. cerevisiae lacks the conserved pathways for copy number control via transcriptional and post-transcriptional gene silencing found in other eukaryotes, Ty1 copy number control must be via another mechanism whose features are outlined. Ty1 response to stress also implicates activation at both transcriptional and postranscriptional steps of Ty1. Finally, we provide several insights in the role of Ty elements in chromosome evolution and yeast adaptation and discuss the factors that might limit Ty ectopic recombination.
© 2005 S. Karger AG, Basel
Request reprints from Pascale Lesage, CNRS UPR 9073
Institut de Biologie Physico-Chimique
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Supported by the Centre National pour la Recherche Scientifique (UPR 9073), the Université Paris VII and the Association pour la Recherche contre le Cancer (grant no. 4663 to P.L.). A.L.T. is the recipient of a doctoral fellowship from the French Ministère de la Recherche.
Manuscript received 16 December 2003;
accepted in revised form for publication by J.-N. Volff 18 March 2004.
Number of Print Pages : 21
Number of Figures : 4, Number of Tables : 3, Number of References : 175
Cytogenetic and Genome Research
Vol. 110, No. 1-4, Year 2005 (Cover Date: 2005)
Journal Editor: H.P. Klinger, Bronx, N.Y.; M. Schmid, Würzburg
ISSN: 1424–8581 (print), 1424–859X (Online)
For additional information: http://www.karger.com/cgr