Armadillo/Pangolin regulates PCNA and DREF promoter activities.

Here we show that Armadillo and Pangolin (dTCF), downstream effectors of the Wingless (Wg) signal transduction pathway, activate transcription of the important DNA replication-related genes encoding Drosophila proliferating cell nuclear antigen (PCNA) and DNA replication-related element-binding factor (DREF). By transient luciferase expression assays and band mobility shift assays, we demonstrated the PCNA gene to be a direct target gene for the Armadillo/Pangolin complex. Using a GAL4-UAS system, stimulation of the PCNA gene by Armadillo/Pangolin was confirmed in adult females. From the published reports of an inhibitory role, we expected that Drosophila CREB-binding protein (dCBP) would interfere with activation. However, effects were only observed with the DREF but not the PCNA gene. In the latter case, as in mammals, dCBP could potentiate Armadillo-mediated activation. These results suggest that first, PCNA and DREF genes are targets of the Armadillo/Pangolin complex and second, dCBP modulates Wg signaling in a gene-specific manner.