Insights into dynamics can be gained using live-cell fluorescence microscopy, either via observation of individual fluorophore-labeled chromosomal loci moving throughout the nucleus (Marshall et al. 1997; Heun et al. 2001), or via fluorescence recovery after bleaching (FRAP) studies on the time-scales of diffusion or replacement of proteins in large regions (McNally et al. 2000; Kimura and Cook 2001). At higher resolution, genetically encoded pulse chase schemes have been adapted to allow epigenomic analysis of chromatin dynamics. For example, nucleosome turnover rates have been characterized in budding yeast by inducing expression of epitope-tagged histones and analyzing the localization of the epitope of interest over a time course using ChIP-chip or ChIP-seq (Dion et al. 2007; Jamai et al. 2007; Rufiange et al. 2007), and a related metabolic labeling strategy has been used to similar ends in the fruit fly (Deal et al. 2010). These studies reveal replication-independent turnover at transcribed genes, with more rapid histone replacement occurring at regulatory regions (promoters and enhancers). Similar strategies have been applied to other proteins, including components of the basal transcription machinery (van Werven et al. 2009) and transcription factors (Lickwar et al. 2012).
