Promoters Constrain Evolution of Expression Levels of Essential Genes in Escherichia coli.

Variability in expression levels in response to random genomic mutations varies among genes, influencing both the facilitation and constraint of phenotypic evolution in organisms. Despite its importance, both the underlying mechanisms and evolutionary origins of this variability remain largely unknown due to the mixed contributions of cis- and trans-acting elements. To address this issue, we focused on the mutational variability of cis-acting elements, that is, promoter regions, in Escherichia coli.

Dicer-related drh-3 gene functions in germ-line development by maintenance of chromosomal integrity in Caenorhabditis elegans.

In the course of systematic RNA interference (RNAi)-based screens with helicase-like genes in Caenorhabditis elegans, we have identified the drh-3(D2005.5) gene as a candidate gene for protection against X-ray irradiation. This gene encodes a novel RNA helicase-like protein that is similar to two nematode Dicer-related helicases (DRH).