P transposons controlled by the heat shock promoter.

Abstract

We have transformed Drosophila melanogaster with modified P-element transposons, which express the transposase function from the heat-inducible hsp70 heat shock promoter. The Icarus transposon, which contains a direct hsp7O-P fusion gene, behaved like a very active autonomous P element even before heat shock induction. Although heat shock led to abundant somatic transcription, transposition of the Icarus element was confined to germ line cells. To reduce the constitutive transposase activity observed for the Icarus element, we attenuated the translational efficiency of the transposase RNA by inserting the transposon 5 neomycin resistance gene between the hsp70 promoter and the P-element sequences. The resulting construct, called Icarus-neo, conferred resistance to G418, and its transposition was significantly stimulated by heat shock. Heat shocks applied during the embryonic or third instar larval stage had similar effects, indicating that transposition of P elements is not restricted to a certain developmental stage. Both Icarus and Icarus-neo destabilized snW in a P-cytotype background and thus at least partially overcome the repression of transposition. Our results suggest that the regulation of P-element transposition occurs at both the transcriptional and posttranscriptional levels.Transposable elements are a major cause of genome instability, responsible for a large fraction of spontaneous mutations in Drosophila melanogaster (1,3,7,20,25,26,31,43). The functional analysis of metazoan transposons has been complicated by the fact that transposition events are usually rare and the physiological conditions they require are not well defined. The P elements responsible for the phenomenon of P-M hybrid dysgenesis (21) in D. melanogaster are of particular interest because their transpositional activity, which can be readily detected by genetic tests (14,19,36), is potentially high but under strict genetic control. Transposition is induced at a high frequency only if males carrying functional P elements (P strains) are crossed with females lacking P factors (M strains), but not in the reciprocal or in a P x P cross (for a review, see references 6 and 13). Because the repressed state (P cytotype) is determined by P factors themselves, it has been suggested that P elements code for a negative regulator in addition to transposase function (10, 29).Transposition of P elements is specific for germ line cells since no appreciable activity can be detected in the soma (11,42). It is not known whether this is the result of tissuespecific transcription of P elements or a requirement for germ line-specific host functions acting posttranscriptionally.P elements have been cloned (4, 32) and sequenced (29) and shown to transpose from injected plasmid DNA into the chromosomes of germ line cells (19,33,36 elements can no longer transpose autonomously, they can be mobilized when the missing transposase function is provided in trans by an intact helper element. A functional analysis of P elements was started by Karess and Rubin (1...

DrosophilaP element: Transposition, regulation and evolution

“…The regulatory properties of a number of lines harboring only complete P elements, after genetic transformation, suggested that this type of element is not able to establish the P cytotype (Steller & Pirrotta, 1986;Daniels et al, 1987;Preston & Engels, 1989). Gloor et al (1993) have analyzed a large number of lines harboring one single de novo insertion of a complete P element, generated by transposition.…”

Functional and bioinformatics analyses reveal conservation of cis‐regulatory elements between sciaridae and drosophilidae

“…Embryos of the D. melanogaster y,w recipient strain were injected with both the phsp helper plasmid (final concentration 0.1 lg/ml) (Steller and Pirrotta, 1986) and the tested constructs (final concentration 0.5 lg/ml), following standard procedures Spradling and Rubin, 1982). Transformed flies were employed to establish homozygous and/or balanced lines.…”

A novel spatial transcription pattern associated with the segmentation gene, giant, of Drosophila.

“…Transposon constructions were assembled in the pUChsneo vector (Steller and Pirrotta, 1986) or in Carnegie 20 (Rubin and Spradling, 1983). Embryos from Df(l)w67c23(2) or r506 flies were injected with a solution containing 400 Stg/ml transposon and 80 uLg/ml phs7r helper plasmid (Steller and Pirrotta, 1986 …”

“…Embryos from Df(l)w67c23(2) or r506 flies were injected with a solution containing 400 Stg/ml transposon and 80 uLg/ml phs7r helper plasmid (Steller and Pirrotta, 1986 …”