LAUSR

Genomes are more than one-dimensional entities purely defined by their linear DNA sequences [Misteli T, Cell (2007)]. A long standing challenge in biology is to decipher the principles of organization of what can be considered, by analogy with human-created libraries, the cell's primary unit of information storage and retrieval. In this respect, the development of super-resolved fluorescence microscopy has provided a new toolbox to peer into the nucleus. For instance, super-resolution microscopy has been recently applied to the investigation of nanoscale chromatin architecture, revealing nucleosome higher-order organization into heterogeneous ‘clutches’ and epigenetically dependent folding motives [Ricci M et al, Cell, (2015); Boettiger A et al, Nature (2016)].However, dynamic properties of proteins in the nucleus are also critical for their function [Misteli T, Cell (2007)]. Fluorescence Correlation Spectroscopy (FCS) has been used to map the dynamics of several proteins in the nucleus with diffraction-limited spatial resolution. Here we combine a novel STED-based super-resolution method [Lanzano’ L et al, Nat Commun (2015)] with FCS to measure protein dynamics in the nucleus with an improved spatial resolution of about 100 nm. We sample several positions within the nucleus by performing line scanning. The measured spatial and temporal heterogeneity of the dynamics, quantified by a recently introduced algorithm [Scipioni L et al, Biophys J (2016)], is discussed in relation to nuclear organization.