Dominant suppressor genes of p53-induced apoptosis inDrosophila melanogaster

Abstract

SummaryApoptosis, the programmed cell death, is responsible for the removal of cells seriously damaged or unwanted in development. A major function of apoptosis is the removal of cells which suffered oncogenic mutations, thereby preventing cancerous transformation.By making use of theDEPtransposon, aPelement derivative made in our laboratory, we made an insertional mutagenesis screen inDrosophila melanogasterto identify genes which, when overexpressed, suppress thep53-activated apoptosis. TheDEPelement has Gal4-activatable, outward-directedUAS-promoters at both ends which can be deleted separatelyin vivo. In theDEPinsertion mutants, we used theGMR-Gal4driver to induce transcription from bothUAS-promoters and tested the suppression effect on the apoptotic rough eye phenotype generated by an activatedUAS-p53transgene.ByDEPinsertions, seven genes were identified which suppressed thep53-induced apoptosis. In four mutants, the suppression effect was resulted by single genes activated by oneUAS-promoter (Pka-R2, Rga, crol, Spt5). In the other three (Orct2, Polr2M, stg), deleting eitherUAS-promoter eliminated the suppression effect. In qPCR experiments we found that the genes in the vicinity of theDEPinsertion also showed an elevated expression level. This suggested an additive effect of the nearby genes on suppressing apoptosis.In the eucaryotic genomes there are co-expressed gene clusters. Three of theDEPinsertion mutants are included and two are in close vicinity of separate co-expressed gene clusters. This raises the possibility that the activity of some of the genes in these clusters may help the suppression of the apoptotic cell death.