Abstract
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.
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Communicated by R. Paro
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Supplementary Figure 1
Eye color phenotypes of ln(1)w m4 stock, a classic hPEV allele. Su(var)s increase the frequency of the suppressed phenotype (b), while E(var)s increase the frequency of the variegated phenotype (a) in the progeny (JPEG 104 kb)
Supplementary Table 1
Testing the P-Sal-M* mutations for antimorphic effect on P-Sal (DOC 68 kb)
Supplementary Table 2
Effect of P-Sal-M* mutants on P{hsp26-pt-T}ci 2-m1021.R eye color (DOC 68 kb)
Supplementary Table 3
Effect of P-Sal-M* mutants on P{hsp26-pt-T}39C-12 eye color variegation (DOC 68 kb)
Supplementary Table 4
Effect of P-Sal-M* mutants on E1 (DOC 67 kb)
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Sameny, A., La, A., Hanna, S. et al. Point mutations in a Drosophila P element abolish both P element-dependent silencing (PDS) of a transgene and repressor functions. Chromosoma 120, 573–585 (2011). https://doi.org/10.1007/s00412-011-0332-y
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DOI: https://doi.org/10.1007/s00412-011-0332-y