Effects of Genomic Position on the Expression of Transduced Copies of the white Gene of Drosophila

Abstract

The white gene of Drosophila is expressed normally when introduced at many different sites in the genome by P-element-mediated DNA transformation, but is expressed abnormally when inserted at two particular genomic positions. It is now demonstrated that the mutant expression in these two cases is caused by the surrounding chromosomal region into which the white gene has been inserted. The white gene could be moved from these two positions, where it confers a mutant phenotype, to other positions in the genome where it confers a wild-type phenotype. However, flies in which white has been moved to one new location have an unusual mosaic phenotype.

Analysis of cis-acting requirements of the Rh3 and Rh4 genes reveals a bipartite organization to rhodopsin promoters in Drosophila melanogaster.

“…One line, P[Rh3.2600CAT]4, exhibits unusually high CAT activity in both the body and the head, although the proper cell-type specificity is preserved within the photoreceptors. The behavior of this line typifies the occasional position effect associated with P-element-mediated germ line transformation (Spradling and Rubin 1983;Hazelrigg et al 1984;Levis et al 1985).…”

Exploiting position effects and the gypsy retrovirus insulator to engineer precisely expressed transgenes

“…However, one parameter that has not been well controlled for in most transgenic experiments is the effects of surrounding host chromatin on transgene expression. These effects, collectively referred to as 'position effects' , determine whether basal expression of the transgene is tight or leaky and whether induced expression of the transgene is sufficiently high to produce detectable phenotypes [3][4][5][6][7] . In most transgenic experiments, such as those based on the pronuclear or embryonic injection of linear DNAs in the mouse 8 and P elements in Drosophila 9 , transgenes randomly integrate into the genome, with only a fraction fortuitously landing into loci with favorable position effects.…”

polyhomeotic regulatory sequences induce developmental regulator-dependent variegation and targeted P-element insertions in Drosophila.

“…Normally, variegated eyes are observed when a chromosomal rearrangement places the euchromatic white gene next to heterochromatin, and this phenomenon is called positioneffect variegation (PEV) (for reviews, see Eissenberg 1989;Henikoff 1990;Tartof and Bremer 1990;Reuter and Spierer 1992 (Hazelrigg et al 1984;Levis et al 1985). No more than 1% of anomalous expression of white was detected when hundreds of lines carrying a P-lacW insertion were made (Dura et al 1993).…”