Structure-function analysis of Cdc25^Twine degradation at the Drosophila maternal-to-zygotic transition

Downregulation of protein phosphatase Cdc25^Twine activity is linked to remodelling of the cell cycle during the Drosophila maternal-to-zygotic transition (MZT). Here, we present a structure-function analysis of Cdc25^Twine. We use chimeras to show that the N-terminus regions of Cdc25^Twine and Cdc25^String control their differential degradation dynamics. Deletion of different regions of Cdc25^Twine reveals a putative domain involved in and required for its rapid degradation during the MZT. Notably, a very similar domain is present in Cdc25^String and deletion of the DNA replication checkpoint results in similar dynamics of degradation of both Cdc25^String and Cdc25^Twine. Finally, we show that Cdc25^Twine degradation is delayed in embryos lacking the left arm of chromosome III. Thus, we propose a model for the differential regulation of Cdc25 at the Drosophila MZT.