Reverse transcriptase and integrase of the <i>Saccharomyces cerevisiae </i>Ty1 element

Abstract

Integrase (IN) and reverse transcriptase (RT) play a central role in transposition of retroelements. The mechanism of integration by IN and the steps of the replication process mediated by RT are briefly described here. Recently, active recombinant forms of Ty1 IN and RT have been obtained. This has allowed a more detailed understanding of their biochemical and structural properties and has made possible combined in vitro and in vivo analyses of their functions. A focus of this review is to discuss some of the results obtained thus far with these two recombinant proteins and to propose future directions.

The Ty1 LTR-Retrotransposon of Budding Yeast,Saccharomyces cerevisiae

“…During the integration process, Ty1 IN catalyzes a nucleophilic attack by the 3′ OH moieties at the blunt ends of the cDNA molecule on each strand of the target DNA at 5-bp staggered sites. These concerted transesterification reactions, called the strand transfer step (reviewed in [174]), result in a newly exposed 3′ OH and 5-nucleotide gap on each strand of the target DNA at the cDNA:target DNA junctions. Repair of the gaps generates a 5-bp target site duplication (TSD) flanking the newly integrated Ty1 cDNA, which is a hallmark of Ty1 integration.…”

Flexible Nature and Specific Functions of the HIV-1 Nucleocapsid Protein

“…8 In fact, many ERV copies are present in the genome of most vertebrates and in invertebrates such as the Gypsy retrovirus in the insect Drosophila 9 and the transposons Tys in yeast. 10 In addition, non-LTR elements, such as LINEs that replicate by a copyand-paste process involving reverse transcription, constitute a large fraction of the genome of higher eukaryotes. 11 The ERVs and, more generally, the endogenous retroelements that are abundant in eukaryotic genomes are thought to contribute to genome plasticity and to protect the host against infection by related pathogenic retroviruses.…”

Ty1 integrase overexpression leads to integration of non-Ty1 DNA fragments into the genome of Saccharomyces cerevisiae

“…During the integration process, Ty1 integrase creates a 5-bp staggered cut in the target DNA and joins the ends of the blunt-ended cDNA molecules to the exposed 5′ phosphate groups of the target in a transesterification reaction (reviewed by Wilhelm et al 2005). It is generally assumed that the conserved inverted dinucleotides 5′-TG-CA-3′ at the ends of the cDNA duplex are absolutely required for transposition in vivo, although only few sequence alterations have been investigated (Sharon et al 1994).…”

“…It has been suggested that host cell factors may contribute to substrate specificity in vivo (Wilhelm et al 2005; Moore and Garfinkel 2000). Indeed, in a recent study of non-homologous integration (NHI; Schiestl and Petes 1991; Schiestl et al 1993, 1994; Zhu and Schiestl 1996) in yku70 mutants we observed several examples where plasmid DNA was integrated into genomic DNA by a process apparently mediated by Ty1 integrase (Kiechle et al 2000).…”