In most living cells, chromosomes are formed from highly condensed DNA and basic proteins that function to compact the chromosomes into a structure called chromatin. This research is focused on understanding the multitude of critically important roles chromatin structure plays in normal development. In particular, the work focuses on a highly conserved group of proteins that form a complex whose main function is to regulate gene expression through direct effects on chromatin structure. This complex uses energy to alter the contacts between chromosomal DNA and histones (basic proteins that wrap DNA in the cell) to allow for specific changes in gene expression. This energy driven process is called 'chromatin remodeling'. When components of this complex are missing or mutated, cells lose the ability to properly control their fates and growth, leading to a variety of defects in proper body patterning and unregulated cellular proliferation. This project utilizes molecular genetics and biochemical assays to explore important connections between hormone signaling and chromatin remodeling during development. Hormone signaling directs the development of tissues to adopt certain fates. Using both classical and 'reverse' (making specific mutations in the genes under study) genetics and cell-culture based studies, the mechanisms are being defined by which hormone receptors select the genes they will regulate and how they cooperate with chromatin remodeling complexes to either turn genes on or off in response to the presence of hormone signals. Genetic interactions are being examined between genes important for hormone signaling and the genes that help convey those signals to the proper cellular targets. The genes important in this process are also being selectively silenced in cultured cells where it is possible to directly address how the chromatin remodeling complexes help to determine whether certain genes will be activated or repressed. The project utilizes molecular, genetic and biochemical analyses of the Drosophila melanogaster (fruitfly) Brahma (Brm) chromatin remodeling complex. Research efforts are primarily focused on one of the most highly conserved and critically important components, known as SNR1. This subunit is crucial in both flies and humans for coordinating or targeting specific protein interactions between the complex and a variety of transcription factors and cell cycle regulatory proteins. The broader scientific impacts of these studies are: (1) teaching and training of graduate and undergraduate students in fundamental concepts of systems biology, including molecular genetics, biochemistry, and bioinformatics/structural biology; and (2) a better understanding of the functional relationships among subunits of a large and extremely important chromatin remodeling complex. This project also provides new insights into the biological significance of chromatin remodeling in normal developmental processes, including hormone-dependent gene regulation and control of cell growth.
