Biologjia Online

The stability and intracellular localisation of ß-catenin (also known as Armadillo in flies) is a central control point in Wnt signalling. Now, on p. 1819, Hayward and co-workers report a surprising way in which the activity of Armadillo/ß-catenin might be regulated – by Notch. Their genetic and biochemical experiments in developing Drosophila and in cultured fly and mouse cells indicate that Notch modulates Wnt signalling – an idea that has previously attracted some controversy – by regulating Armadillo/ß-catenin activity. This regulation occurs independently of the interaction of Notch's active intracellular domain with Suppressor of Hairless, an interaction needed for the transcriptional regulation of many of Notch's previously recognised targets. The researchers suggest that the modulation of Armadillo/ß-catenin activity by Notch both establishes a threshold for Wnt signalling and stringently regulates activated Armadillo/ß-catenin, a function that is relevant to Notch's tumour suppressor role in mouse skin.