RSC remodeling of oligo-nucleosomes: an atomic force microscopy study

TL;DR

This study uses Atomic Force Microscopy to analyze how the RSC chromatin remodeling factor mobilizes oligonucleosomes, revealing non-directional nucleosome movement and nucleosome packing at DNA edges, which may help overcome nucleosomal barriers.

Contribution

First quantitative AFM analysis of RSC-induced remodeling on oligonucleosomes, elucidating mechanistic features and final nucleosome arrangements.

Findings

RSC causes nucleosomes to pack at DNA edges.

No preferred directionality in nucleosome movement was observed.

Remodeling results in nucleosome depletion of large DNA stretches.

Abstract

RSC is an essential chromatin remodeling factor that is required for the control of several processes including transcription, repair and replication. The ability of RSC to relocate centrally positioned mononucleosomes at the end of nucleosomal DNA is firmly established, but the data on RSC action on oligo-nucleosomal templates remains still scarce. By using Atomic Force Microscopy (AFM) imaging, we have quantitatively studied the RSC- induced mobilization of positioned di- and trinucleosomes as well as the directionality of mobilization on mononucleosomal template labeled at one end with streptavidin. AFM imaging showed only a limited set of distinct configurational states for the remodeling products. No stepwise or preferred directionality of the nucleosome motion was observed. Analysis of the corresponding reaction pathways allows deciphering the mechanistic features of RSC-induced nucleosome relocation. The final outcome of RSC remodeling of oligosome templates is the packing of the nucleosomes at the edge of the template, providing large stretches of DNA depleted of nucleosomes. This feature of RSC may be used by the cell to overcome the barrier imposed by the presence of nucleosomes.