Skip to main content
Open Access Publications from the University of California

UC San Diego

UC San Diego Electronic Theses and Dissertations bannerUC San Diego

Identification of the Prenucleosome and Analysis of the Mechanism of ATP-Dependent Chromatin Assembly /


The assembly of chromatin is a necessary process that must occur following DNA-utilizing processes, such as replication, repair, and transcription. Chromatin is a complex of DNA and proteins that is responsible for packaging and organizing DNA into the eukaryotic nucleus and also serves as a regulator of all DNA-utilizing processes. The basic repeating unit of chromatin is the nucleosome, which consists of approximately 147 base pairs of DNA wrapped around a histone octamer core. Chromatin assembly is facilitated by core histone chaperones and ATP -dependent motor proteins. For this dissertation, I have investigated the mechanism of chromatin assembly using a purified, defined in vitro chromatin assembly system, consisting of relaxed DNA, ATP, core histones, the histone chaperone NAP1, and the ATP-driven motor proteins ACF or CHD1. A novel nonnucleosomal histone-DNA complex, termed the prenucleosome, was identified as an intermediate of chromatin assembly. Whereas this intermediate of chromatin assembly is biochemically distinct from canonical nucleosomes, the prenucleosome is indistinguishable from a nucleosome by atomic force microscopy. Analysis of chromatin remodeling-defective mutants of CHD1 demonstrated that ATP-dependent chromatin assembly is a distinct activity from chromatin remodeling. These findings indicate a multi-step mechanism for chromatin assembly. Histone chaperones first deposit histones onto DNA to generate prenucleosomes. These prenucleosomes are subsequently converted into randomly-positioned canonical nucleosomes by ATP-dependent motor proteins. Lastly, ATP- driven motor proteins reposition these nucleosomes into periodic arrays. Altogether, these studies provide new insight into the mechanism of ATP-dependent chromatin assembly, highlighting the necessity of ATP-driven motor proteins in this process

Main Content
For improved accessibility of PDF content, download the file to your device.
Current View