Cells copy their DNA each time they divide in a process that is carefully controlled by specialized proteins that are found in fungi, insects, and other animals. In insects, one of these key regulators of DNA replication has evolved a second essential role to chemically modify chromosomal proteins. This project seeks to understand how and why these two functions are combined within a single gene, since this could provide a mechanism to coordinate DNA replication with other chromosomal processes. In the long term, this research could identify novel targets for insecticides, and could also enhance our understanding of how DNA replication and gene expression are controlled and coordinated in different organisms. Graduate students will be trained as part of this project, which also provides an undergraduate course-based research experience (CURE). This CURE aims to involve undergraduate students in authentic research experiences as early as possible during their university career to enhance their academic performance, retention in Science, Technology, Engineering and Math (STEM), and improve their laboratory research skills.
DNA replication is initiated by the action of two kinases, CDK and Cdc7, which both require binding of regulatory subunits for activity. Dbf4 is the regulatory subunit for Cdc7, and loss of either of these subunits disrupts DNA replication and mitosis in organisms from yeast to mammals. Previous studies showed that Chiffon, the single identifiable Dbf4 homolog in Drosophila, binds and activates Drosophila Cdc7 (dCdc7). In contrast to dCdc7, which is essential for DNA replication and viability, the dCdc7-binding activity of Chiffon is not required for development. Instead, Chiffon has a second replication-independent function that is essential; it binds Gcn5 and nucleates formation of an insect-specific histone acetyltransferase complex, Chiffon Histone Acetyltransferase (CHAT). Surprisingly, CHAT can substitute for the well characterized Gcn5 transcriptional coactivator Spt-Ada-Gcn5 acetyltransferase (SAGA) during development. Since the histone acetyltransferase activity of SAGA stimulates transcription, the hypothesis of this project is that histone acetylation by CHAT is necessary for proper transcription activation of genes that are essential for Drosophila growth and development. This project will identify genes that require CHAT for proper gene expression, characterize the genome-wide distribution of CHAT, and explore the mechanisms that control cell type-specific expression of the DDK versus CHAT complexes. Overall, these studies will provide insight into the dynamics and spatiotemporal coordination of genome replication, chromatin modification and transcription.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
