Chromatin dynamics and gene positioning

Abstract

The mammalian cell nucleus provides a landscape where genes are regulated through their organization and association with freely diffusing proteins and nuclear domains. In many cases, specific genes are highly dynamic, and the principles governing their movements and interchromosomal interactions are currently under intensive study. Recent investigations have implicated actin and myosin in chromatin dynamics and gene expression. Here, we discuss our current understanding of the dynamics of the interphase genome and how it impacts nuclear organization and gene activity.

Figure 1. Chromosome Territories and Nuclear Bodies

A depiction of the mammalian cell nucleus showing chromosome territories and various nuclear bodies.

Figure 2. Interchromosomal Interactions and Gene Expression

Model for steroid-induced interchromosomal interactions and enhanced transcription at a nuclear speckle (Nunez et al., 2008). Upon treatment with the hormone 17β-estradiol (E₂) a basal level of TFF1 (yellow) and GREB1 (red) expression is observed (A). Over time (2 min–60 min) an interchromosomal association is observed between TFF1 and GREB1 via actin/myosin interactions (B and C). These interactions result in enhanced levels of gene expression (B and C). It remains to be determined if the interacting genes recruit pre-mRNA splicing factors from pre-existing speckles (B) or if the genes move to an existing speckle (C).