Developmental Functions of SNR1 and the BRM Chromatin Remodeling Complex in Drosophila

Loyola University Of Chicago, Health Sciences Campus, Maywood IL

Investigators

Abstract

Intellectual merit of the project: Access to genetic information embedded within the genome is essential for the proper development of all eukaryotic organisms from simple yeast to vertebrate animals; thus, it is of great importance to understand the cellular processes that guide proper gene regulation in vivo. Several key steps involved in gene regulation require chromatin remodeling, defined as the alteration of DNA-Histone contacts that comprise the basic building blocks of the genome. Recent advances have revealed that chromatin remodeling "complexes" that include multiple proteins are essential cofactors in initiating transcription on chromosomal templates during development, as well as the regulation of alternative splicing and epigenetic control of gene expression. Although considerable progress has been made in recent years in our understanding of the biochemical mechanism of chromatin remodeling, fundamental questions remain as to how chromatin remodeling complexes are targeted to certain genes in vivo and how they contribute mechanistically to both transcription activation and repression. This project explores the role of the Drosophila Brahma (SWI/SNF) chromatin remodeling complex in coordinating hormone signaling with gene regulation at developmentally appropriate time points through effects on transcript elongation by RNA Polymerase II--an exciting and unexpected role only recently discovered. The Drosophila SNR1 and BRM proteins are core components of the Brahma complex, which is highly conserved among all eukaryotes. This project uses unique genetic and biochemical tools in both fruitflies and cultured cell systems to unravel the functional relationships among complex components, including the ATPase subunit BRM and the critical regulatory subunit, SNR1. These analyses will help to define the mechanisms of in vivo target gene selection and regulation by chromatin remodeling complexes. The relationships between the Brahma complex and nuclear receptor coactivators that direct the hormone response pathway are also the focus of this investigation. While coactivator complexes have been identified in both insects and vertebrates and there are strong links between chromatin remodeling and coactivator function, the biological roles of individual components are poorly understood. This project focuses on a biological analysis of the cmi gene, encoding a conserved homolog of the N-terminal portion of the mammalian ALR1/MLL2 protein found as a component of several nuclear receptor coactivator complexes. Through the deployment of recently generated genetic tools this project will enable an unprecedented dissection of the normal functions of cmi. These analyses will provide an important model system to help understand coactivator functions in metazoan development and the relationship with chromatin remodeling. These studies using Drosophila as a genetic model system will provide greater understanding of the basic mechanisms by which chromatin remodeling complexes participate in programming gene expression during development, as the regulatory systems in flies and vertebrates are remarkably similar, including transcription control and nuclear receptor function. Thus, the results of this project should provide important insights to help biologists better understand chromatin remodeling functions as well as the regulation of RNA polymerase elongation in diverse systems. Broader impact of the project. Graduate (both MS and PhD), undergraduate and several high school students directly participate in the research projects and are trained by the PI and senior personnel. Women and minorities are highly represented. Multidisciplinary training is a vital aspect of education to prepare students for diverse science careers and this project takes full advantage of the unique tools currently available for Drosophila research. Students are trained in molecular and developmental genetics, biochemistry, molecular biology and bioinformatics/structural biology. Student research (both graduate and undergraduate) is frequently included in publications. Students are encouraged to present their work at local, regional and national meetings and to collaborate with expert investigators outside the institution to enhance their training experience.