DOSAGE COMPENSATION IN DROSOPHILA AND THE COMPLEX WORLD OF TRANSCRIPTIONAL REGULATION

The purpose of this review is to draw attention to the mechanism of do sage compensation in Drosophila as a model for the study of the regula tion of gene activity through the modulation of transcription. Dosage compensation resembles some mechanisms of transcriptional regulation, found in widely divergent organisms, that do not play a role in the ac tivation of silent genes but determine the level of activity of genes that have been induced through the action of specific activators. It d iffers from other known regulatory mechanisms in that its effect is to achieve, on average, a twofold change in gene activity levels. This r eview introduces the notion that, in order to yield such a defined lev el of regulation, the mechanism of dosage compensation in Drosophila, and perhaps in Caenorhabditis as well, incorporates elements that gove rn both transcriptional enhancement and repression within the same mul ti-protein regulatory complex.