Precise and imprecise somatic excision of the transposon Tcl in the nematodeC.elegans

Abstract

Eleven chromosomal products of somatic excision of Tc1 transposable elements have been cloned and sequenced. The cloning method did not involve genetic reversion; therefore the products analyzed should be representative. Six empty religated target sites were from excision of one Tc1 element inserted near actin genes on linkage group V; five were from a second Tc1 element inserted elsewhere on the same linkage group. All six products from the first element were identical in sequence to an empty target site from a second strain, indicating excision had been precise. Two of the products from the second element were also precise, whereas the other three contained four extra nucleotides at the point of excision, indicating an imprecise excision. The four nucleotides are the same in all cases and could represent two terminal nucleotides of the transposon plus a two-nucleotide target site duplication. The difference in the ratio of precise to imprecise excision at the two insertion sites suggests a possible chromosomal position effect on the pathway of Tc1 somatic excision.

Targeted engineering of the Caenorhabditis elegans genome following Mos1-triggered chromosomal breaks

“…The first class of events generated small footprints ranging from the insertion of few bases contained in the 3′‐PSS to the deletion of fewer than 10 bases immediately flanking the break point. Such footprints are very similar to those usually observed after DNA transposon excision (see, for instance, examples reported for Mos1 in Drosophila (Bryan et al , 1990), Tc1 and Tc3 in C. elegans (Ruan and Emmons, 1987; Plasterk, 1991; Plasterk and Groenen, 1992; van Luenen et al , 1994) or Sleeping Beauty in mammalian cells (Fischer et al , 2001; Izsvak et al , 2004)), and are typical of repair by canonical NHEJ. These events were prominent in somatic cells, where they required Ku80 and ligase IV activities.…”

The origin of footprints of the Tc1 transposon of Caenorhabditis elegans.

“…Transposition and excision of Tc elements in the germ line of Caenorhabditis elegans require the presence of a 'mutator' gene Waterston, 1984 andHerman and Shaw, 1987;Ruan and Emmons, 1987;Eide and Anderson, 1988;Kiff et al, 1988;Mori et al, 1988). The molecular nature of the mutator is unknown; it could be a Tcl variant that differs from other elements in primary sequence or surrounding sequences .…”

Somatic reversion of P transposable element insertion mutations in thesingedlocus ofDrosophila melanogasterrequiring specific P insertions and atrans- acting factor

“…P-elements in hybrid dysgenesis move so much more frequently than most other animal transposable elements which have been studied in detail that it is still not clear whether their restriction of movements to germ cells is typical of animal transposable elements. The Caenorhabditis elegans Tel element (Emmons & Yesner, 1984;Ruan & Emmons, 1987;Moerman, Benion & Waterston, 1986) and the Drosophila mauritiana mariner element (Jacobson, Medhora & Hartl, 1986;Bryan, Jacobson & Hartl, 1987) move somatically, as do plant transposable elements (Nevers, Shepherd & Saedler, 1986), although in plants the distinction of the germ line is not clear.…”