Developmental regulation of antisense-mediated gene silencing in Dictyostelium

In Dictyostelium, the expression of antisense transcripts has been successfully used to reduce or eliminate gene expression. In most cases this occurs on the level of RNA stability resulting in a loss of both sense and antisense transcript accumulation. We here show that the antisense effect is regulated during the developmental cycle, i.e., in certain developmental stages and under certain developmental conditions, complementary RNAs appear not to interact with each other, resulting in a failure to abolish expression of the gene of interest. We find that this is not only the case with artificially introduced antisense constructs but also with the endogenous, antisense-regulated PSV-A gene. Our data demonstrate that antisense-mediated gene silencing is conferred by a biochemical machinery that is subject to regulation in vivo. The results provide a basis to better understand this machinery and to dissect the components. They may also explain the failure of some antisense experiments in Dictyostelium and possibly in other organisms.