Transcription of the singed-weak mutation of Drosophila melanogaster: elimination of P-element sequences by RNA splicing and repression of singed transcription in a P genetic background

Abstract

The dysgenesis-induced, hypermutable singed-weak allele has two incomplete P-elements inserted in a head-to-head configuration in the 5' non-coding exon of the singed bristle locus of Drosophila melanogaster. In the presence of P transposase, each element excises to produce single element derivatives, singed-extreme and singed-(+), that have either an extreme bristle or wild-type phenotype, respectively. In an M background, pseudo-wild-type transcripts are made that initiate at the singed promoter, read through the insertions, and are spliced to remove the P-element sequences and part of the 5' exon. The abundance of the pseudo-wild-type RNAs in pupae correlates with the bristle phenotype, being highest in singed-(+) and lowest in singed-extreme. Other RNAs are made that retain the insertions, or are truncated with respect to the downstream coding singed exons and have their 3' ends within the insertions. The mutants are female-fertile in an M background but sterile in a P background where little singed RNA can be detected. Transgenes containing either a complete P-element or an incomplete P-element known as KP impair the fertility of females carrying the singed-weak mutation, suggesting that the proteins encoded by these two widely distributed P-elements may be responsible for inhibiting transcription of singed-weak in a P background.

Cytotype Regulation by TelomericPElements inDrosophila melanogaster: Evidence for Involvement of an RNA Interference Gene

“…These P elements are inserted in a head-to-head orientation 8 bp apart in the 59 region of the singed gene. Furthermore, because their sequences are included within some singed transcripts (Paterson et al 2007), they could possibly generate double-stranded P RNA, which in turn could stimulate an RNAi response to other P RNAs, including the P transposase mRNA. By impairing this response, aub mutations might increase the likelihood that P mRNA will be translated into the P transposase in sn w flies, leading to an increased frequency of P-element excisions from sn w .…”

Reexamining the P-Element Invasion of Drosophila melanogaster Through the Lens of piRNA Silencing

“…Type II repressors reduce the activity of germline-expressed P-LacZ reporters , and both types of repressors reduce the expression of singed-weak, a P-element insertion allele of the germline-expressed gene singed (Roiha et al 1988;Robertson and Engels 1989;Misra et al 1993;Paterson et al 2007). In vitro assays further suggest that type II repressors directly repress transposition through competitive or negative interactions with full-length P transposase (Lee et al 1996(Lee et al , 1998.…”