Abstract
In this chapter, we will learn that nucleosome positioning around TSS regions has an important role on coordinated gene activation of promoter regions. In this context, we will discuss that chromatin modification and remodeling machineries allow the transition from a repressed state to an active state. Chromatin remodeling factors are multiprotein complexes that use the energy of ATP hydrolysis, in order to remodel or remove nucleosomes regulating the exposure of genomic DNA to transcription factors. Global changes in gene expression correlate with spatial chromatin reorganizations that play a significant role during development. Thus, transcriptionally active genes are involved in the process that directs the architecture of the nucleus in differentiated tissues and cell types. In the interchromatin compartment of the nucleus there are subnuclear structures, such as transcription factories, that contain high concentrations of Pol II. Transcription factories function as an attractor for commonly regulated genes with shared nuclear positions. This suggests that the transcriptional status of a gene is based on the position in the sphere of the nucleus.