A repetitive DNA family, conserved throughout the evolution of free-living nematodes.

This paper concerns the molecular evolution of a tandemly repeated DNA family, RcC9, originally identified in Caenorhabditis elegans. The minimum unit of periodicity of this family is the pentanucleotide [nGAAn] and its complement [nTTCn] recurring several times in alternating tandem arrays. This consensus sequence is identical to that of the heat-shock element (HSE). Multiple HSEs are present in the regulatory regions of heat-inducible genes in a wide range of eukaryotic species; HSEs mediate transcriptional activation through the binding of the heat-shock factor (HSF). I describe some repeated DNA families sharing this same consensus and found in nematode species other than C. elegans. Although the consensus is conserved, the repeated sequence diverged between species to the point that cross-hybridization is abolished. Evolutionary implications will be discussed.