A purified mariner transposase is sufficient to mediate transposition in vitro.

Abstract

Mariners are a widespread and diverse family of animal transposons. Extremely similar mariners of the irritans subfamily are present in the genomes of three divergent insect host species, which strongly suggests that species‐specific host factors are unnecessary for mobility. We tested this hypothesis by examining the activity of a purified transposase from one of these elements (Himar1) present in the horn fly, Haematobia irritans. Himar1 transposase was sufficient to reproduce transposition faithfully in an in vitro inter‐plasmid transposition reaction. Further analyses showed that Himar1 transposase binds to the inverted terminal repeat sequences of its cognate transposon and mediates 5′ and 3′ cleavage of the element termini. Independence of species‐specific host factors helps to explain why mariners have such a broad distribution and why they are capable of horizontal transfer between species.

The Tol1 element of the medaka fish, a member of the hAT transposable element family, jumps in Caenorhabditis elegans

“…Manifestation of such a wide distribution leads to the inference that elements of this family require no or few factors produced from host cells for their transposition reaction. This has already been demonstrated with mariner, Tc1 and some other elements: transposition occurs in vitro as long as a purified transposase is provided (Vos et al, 1996;Lampe et al, 1996). It was also inferred and then proven that elements of this family move when they are artificially introduced into organisms other than their original host species.…”

In vivo transposition of mariner -based elements in enteric bacteria and mycobacteria

“…Site specificity can be mediated by transposase binding to the target sequence, interaction with host-or transposon-encoded accessory proteins, DNA supercoiling, or chromosomal structure. The Himar1 transposon has previously been shown to have little site specificity in vitro (11,24). We tested for insertional specificity within the ampicillin resistance gene of a high copy number plasmid and found insertions at almost every TA dinucleotide within the analyzed sequence despite the fact the insertion frequency may be lower in this actively transcribed region than in nontranscribed DNA (1).…”

“…Elements of this superfamily share certain amino acid identities, have similar overall organization, and have similar ''cut-and-paste'' mechanisms of transposition (10)(11)(12). Comparisons of sequences of mariner͞ Tc1 elements from insects strongly suggest that there has been recent horizontal transmission (10) and, by implication, that a single transposon is capable of function in diverse eukaryotic hosts.…”

“…This surprising observation suggested that it might be possible to reconstitute transposition in vitro. In vitro transposition has been observed by using two transposases of the mariner͞Tc1 superfamily in the absence of any added host cofactors (11,12), a property that has been used to make insertion mutations in naturally competent bacteria (13). In fact, both mariner-like and Tc1-like elements have been used to transfer markers between insects (14-16), and the mariner element Mos1, originally derived from Drosophila mauritania, has been shown to transpose in Leishmania major (17).…”

Transposon Mutagenesis of Trypanosoma brucei Identifies Glycosylation Mutants Resistant to Concanavalin A

“…Transposition occurs via a nonreplicative cut-and-paste mechanism, in which a staggered doublestranded break at each end of the transposable element releases it from the donor DNA molecule, freeing it to be ligated into a staggered cut at the target site (19). Transposition is independent of host-specific factors (20), which has allowed mariner to be used for gene disruption in a variety of organisms, including Leishmania (21), nematodes (22), and vertebrates (23,24).…”