Different sets of genes are activated by p53 upon UV or ionizing radiation in Drosophila melanogaster.

The p53 tumour suppressor plays central role in the maintenance of genome integrity. P53 deficient fruit flies are highly sensitive to ionizing radiation (IR) and show genome instability suggesting that the Drosophila melanogaster p53 (Dmp53) is necessary for the proper damage response upon IR. We found that Dmp53 null fruit flies are highly sensitive to ultraviolet radiation (UV) as well. We analyzed the expression levels of apoptotic genes in wild type and Dmp53 null mutant animals after UV or IR using quantitative real-time RT-PCR. Ark (Apaf-1 related killer) was induced in a Dmp53-dependent way upon UV treatment but not by IR, hid (head involution defective/wrinkled) was induced upon both types of DNA damage, while reaper was induced only upon IR but not UV treatment. Using microarray analysis we identified several further genes that are activated upon UV irradiation in the presence of wild type Dmp53 only. Some but not all of these genes show Dmp53-dependent activation upon IR treatment as well. These results suggest that Dmp53 activates distinct cellular pathways through regulation of different target genes after different types of DNA damage.