Drosophila melanogaster SAP18 protein is required for environmental stress responses.

SAP18, a highly evolutionarily conserved protein, has been proposed to be involved in multiple cellular processes, from gene regulation to mRNA processing. To gain further insight into the role of SAP18, we performed genome-wide expression profiling of dsap18 mutant Drosophila melanogaster embryos and we found that dSAP18 is required for the expression of immune and stress related genes. We show that dSAP18 colocalizes with histone H3 phosphorylation, which has been implicated in the regulation of genes in response to signaling stimuli. dsap18 mutant larvae develop melanotic tumors after heat shock and the viability of dsap18 mutant flies is reduced after fungal infection or in high-salt medium. Altogether, our results indicate that dSAP18 is a key player in transcriptional responses to stress.