CAREER: Linking Structure, Stability and Protection in Protamine Packaged DNA

University Of Kentucky Research Foundation, Lexington KY

Investigators

Abstract

Chromatin (the material of chromosomes) is much more compact and highly organized in the nucleus of sperm cells than in the nucleus of other cells. This high degree of compaction, brought about by the association of the DNA with a class of proteins called protamines, is thought to help protect the DNA from damage. Despite previous research, the mechanisms underlying the tight packaging of DNA by protamines remain poorly understood. The goals of this project are to use a multidisciplinary array of tools to establish fundamental knowledge of the mechanisms by which nature utilizes protamines to package, protect and store DNA in sperm cells. The project spans the disciplines of molecular biology, biochemistry, biophysics and analytical chemistry. The unique properties of protamines also have promise for new biotechnological applications in the creation of novel devices for DNA delivery and the development of biosensor technologies. The multidisciplinary nature of the research will create unique training opportunities for undergraduate and graduate student researchers. The project also includes education in chemistry and biophysics, including the development of massive open online courses (MOOCs). Summer workshops will be created for high school teachers to learn about and actively participate in refining and assessing the proposed MOOC courses to best meet the needs of teachers and their students nationwide. Spermiogenesis is a unique multi-step process resulting ultimately in the replacement of histones by protamines in sperm nuclei to a final volume roughly 1/20th that of a somatic nucleus. The near crystalline organization of DNA in mature sperm is crucial for both DNA delivery and the protection of genetic information due to the absence of DNA repair. The long-term goal of the project is to understand the link between physical compaction, interaction energetics and biochemical driving forces in protamine-DNA complexes. The project will use a variety of structural, biophysical and biochemical methods to evaluate protamine-DNA structure and stability to free radicals in vitro and in vivo. These experiments will provide a realistic model of how protamine chemistry controls sperm chromatin organization and quantitative knowledge of the link between DNA packaging and susceptibility of DNA to reactive oxidative species. Protamines exhibit a combination of phosphorylation sites, disulfide bonds, and zinc ions that make them a uniquely rich system to investigate the physical chemistry and structure of protein/DNA interactions and the structure of DNA in the compacted state. These novel aspects of protamine have potential for expoitation in synthetic systems, and the models developed and tested in this project will make contributions to our understanding of protamine-DNA compaction in sperm chromatin as well as providing insights for biotechnological exploitation of DNA devices.