Caffeine sensitivity in Drosophila melanogaster

Abstract

Besides being the most popular drug in the world, caffeine is an attractive tool used in research to help us answer fascinating scientific questions, because caffeine impinges on a number of molecular pathways. In my research, I used caffeine to study DNA repair pathways and insect xenobiotic detoxification. My work has led to the identification of caffeine-sensitive components of the SMC5/6 complex as critical players conveying resistance to genotoxic stress in Drosophila. We were the first group to isolate mutants of Smc5, Smc6 and MAGE in Drosophila melanogaster and showed that the Smc5/6 complex is not essential for viability but plays a conserved role in protecting against genotoxic agents. Smc5/6 is not required for DNA damage checkpoint response; rather it is involved in homologous recombination repair pathway mediated by Rad51. My other project was aimed at establishing caffeine as a tool to comprehensively study detoxification responses in Drosophila. Using DNA microarray, I measured the transcription response of feeding 8 mM caffeine to wild type larvae, and then derived a set of ~ 48 transcripts that represents a highly significant set of genes affected by caffeine and other xenobiotic treatments such as Phenobarbital (PB), a strong xenobiotic response inducer. Such a condensed “xenobiotic core set” was then used to test whether any of these genes were misregulated in mutants of the JNK or CREB pathways. Because the nature of the Smc5/6 caffeine mutants were not elucidated at the time, I tested whether the caffeine mutants had defects in xenobiotic responses. The ultimate goal was to identify transcription factors that regulate xenobiotic detoxification in Drosophila melanogaster. Another study appeared during my thesis study that showed that dNrf2/Keap1 is a key regulator of detoxification responses in Drosophila. My own analysis did identify this factor too, but also suggested that additional transcriptional regulators likely contribute to the induction of xenobiotic enzymes as well.