Point mutations in a Drosophila P element abolish both P element-dependent silencing (PDS) of a transgene and repressor functions.
The P elements of Drosophila melanogaster are well-studied transposons with both mobilizing and repressor functions. P elements can also variably silence the expression of certain other transgenes through a phenomenon known as P element-dependent silencing (PDS). To examine the role of the P repressor in PDS, we have induced, isolated, and characterized 22 point mutations in an archetype P element called P[SalI]89D. All mutations showed a loss in the ability to silence one or more assays for the PDS phenotype. These mutants also lost the ability to induce the suppression of variegation in P[hsp26-pt-T]39C-12, another P element-dependent phenotype. A subgroup of 11 mutations was further assayed for their ability to act as a P repressor and silence the P element promoter transcribing a lacZ                         (                            +                         ) gene, and this function was lost as well. Taken together, this study supports a model of PDS acting through protein interactions, not RNA, with heterochromatic proteins to modify the extent of variegation seen in PDS. Furthermore, the common loss of functions for PDS and P repressor silencing (from another P promoter) argues for a common role of the repressor. This makes the PDS model a good system for examining P repressor functions and how they relate to transposon-mediated gene silencing in general.
Department of Biological Sciences, University of Alberta, Edmonton, Canada.
Alireza
A
Sameny
Anderson
A
La
Scott
S
Hanna
John
J
Locke
D000818:Animals; D004251:DNA Transposable Elements; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D020868:Gene Silencing; D017354:Point Mutation; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D019076:Transgenes
D004251:DNA Transposable Elements; D029721:Drosophila Proteins; D012097:Repressor Proteins