Directional gene silencing induced by a complex subtelomeric satellite from Drosophila

Abstract

The telomeric regions in Drosophila cause transcriptional silencing of integrated transgenes. A complex satellite has recently been identified in the subterminal region of the left arm of chromosome 2 that is a good candidate for the source of the observed telomeric silencing, because genetically marked transposable elements that have inserted into this subtelomeric array show repression and variegation of the reporter gene. We asked whether this satellite can also cause transcriptional repression in ectopic chromosomal positions by placing it upstream of a mini-white reporter gene in P element constructs used for germ line transformation. The transgenes are shielded from external influences at the integration site using SU(HW) binding sites at either end. It was found that the satellite represses transcription of the reporter gene in an orientation dependent and an array length dependent manner. The satellite does not, however, induce variegation under the conditions used. The repressed transgenes do not respond to typical modifiers of centromeric position effect variegation, such as Su(var)205 5 , Su(var)2±1 1 , Su(var)3±1 1 , and Su(var)3±6 1 , or to the addition of a Y chromosome. However, as with the original variegating telomeric insertion, suppression in the transgenes is relieved by Su(z)2 5 , suggesting that suppression induced by the subtelomeric satellite retains aspects of telomeric silencing in ectopic positions.

Construction and Characterization of a Repetitive DNA Library in Parodontidae (Actinopterygii: Characiformes): A Genomic and Evolutionary Approach to the Degeneration of the W Sex Chromosome

“…4,[28][29][30][31][32] Furthermore, previous studies reported the participation of these sequences in chromosomal rearrangements associated with karyotype diversification events and the differentiation of sex chromosomes. [33][34][35][36][37] New methods of next-generation genomic sequencing generated a large amount of information, providing extensive data related to the DNA sequences of organisms; however, arranging the position of repetitive sequences is extremely difficult.…”

Two Distinct Domains in Drosophila melanogaster Telomeres

“…TAS is likely to be directly involved in silencing telomeric transgenes, suggesting a heterochromatic character (Levis et al 1993;Cryderman et al 1999;Golubovsky et al 2001;Karpen and Spradling 1992). Indeed, a 6-kb 2L TAS array exhibited array-length-dependent and orientation-dependent repression of a w reporter gene (Kurenova et al 1998), and a single 1.2-kb region derived from the 1.8-kb X TAS repeat induced pairingsensitive repression of a reporter gene (Boivin et al 2003). Telomeric silencing is different from silencing that occurs in closely linked copies of mini-white genes (Dorer and Henikoff 1994), because TPE on the major autosomes does not respond to mutations in Su(var)205, the gene that encodes HP1 (Wallrath and Elgin 1995;Cryderman et al 1999).…”

Drosophila telomeres: an exception providing new insights

“…Transgenic experiments with P-element constructs bearing a 2L TAS array adjacent to a miniwhite reporter gene revealed that TAS silencing is array-length and orientation dependent (81). Similarly, a 1.2 kb fragment from the X-TAS is also able to silence an adjacent transgenic mini-white gene (82).…”