Gene expression homeostasis and chromosome architecture.

In rapidly growing populations of bacterial cells, including those of the model organism Escherichia coli, genes essential for growth--such as those involved in protein synthesis--are expressed at high levels; this is in contrast to many horizontally-acquired genes, which are maintained at low transcriptional levels. (1) This balance in gene expression states between 2 distinct classes of genes is established by a galaxy of transcriptional regulators, including the so-called nucleoid associated proteins (NAP) that contribute to shaping the chromosome. (2) Besides these active players in gene regulation, it is not too far-fetched to anticipate that genome organization in terms of how genes are arranged on the chromosome, (3) which is the result of long-drawn transactions among genome rearrangement processes and selection, and the manner in which it is structured inside the cell, plays a role in establishing this balance. A recent study from our group has contributed to the literature investigating the interplay between global transcriptional regulators and genome organization in establishing gene expression homeostasis. (4) In particular, we address a triangle of functional interactions among genome organization, gene expression homeostasis and horizontal gene transfer.