Defining Barriers to Nucleosome Mobility through Single-Molecule Manipulation

About This Grant

Chromosomes consist of long DNA strands that hold the information coding for life. Chromosomes are extensively wrapped into spool-like structures called nucleosomes in all plants and animals, including humans. Nucleosome packaging provides the sophisticated levels of control needed for turning genes on and off and regulating cellular functions. This project is focused on understanding how nucleosomes slide along DNA and enable dynamic changes in its packaging. Nucleosomes can be actively moved by special enzymes called chromatin remodelers, but nucleosomes can also spontaneously slide within chromosomes. It is currently unclear how easily nucleosomes slide on natural DNA sequences, and how their mobility may be affected by other cellular factors. Nucleosomes are displaced and chromatin remodelers are often disrupted in diseases such as cancer; therefore, new information on nucleosome sliding will advance understanding of fundamental cellular processes important for human health. A new technique has been developed for this research that allows sensing of the force required to mechanically shift nucleosomes along DNA. This technique should be broadly useful to the scientific community for studying how chromosome-interacting factors affect DNA packaging. This project will offer research training opportunities for students in biochemical and biophysical science and includes outreach activities centered on DNA to engage middle school students in STEM. This project is designed to reveal how intrinsic mobility of the histone core on DNA is affected by DNA sequence, histone variants, and exogenous factors like RNA, transcription factors, and linker histones. This work will also determine the processivity and translocation speeds of ATP-dependent chromatin remodelers as they push nucleosomes along long DNA segments. These goals will be addressed by a combination of biochemistry, next-generation sequencing, and optical trap experiments. The results of these studies will provide new information about how nucleosomes are organized in native sequence contexts and reveal new ways of understanding how histone-DNA interactions intrinsically influence chromatin reorganization. This project is supported by the Genetic Mechanisms and Molecular Biophysics programs in the Molecular and Cellular Biosciences Division of the Biological Sciences Directorate and by the Chemistry of Life Processes program in the Chemistry Division of the Mathematical and Physical Sciences Directorate. 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.