The Differentially Expressed 16-kD Heat Shock Genes ofCaenorhabditis elegansExhibit Differential Changes in Chromatin Structure during Heat Shock

摘要

ABSTRACTThe 16-kD heat shock genes ofCaenorhabditis elegansare encoded by four highly similar genes, arranged as divergently transcribed pairs. In spite of the high level of identity that exists between the HSP16 genes, after 2 hr of heat shock the mRNA from one locus accumulates at 7–14 times the level of that from the other locus. To determine if differential HSP16 gene transcriptional activity contributes to these differences, we examined the chromatin structure of the HSP16 genes in nonshocked embryos and in embryos undergoing both the initial phases of heat shock and after 2 hr of heat shock. To carry out these studies, we developed a nuclei isolation procedure that has allowed us to prepare large amounts of nuclei fromC. elegansembryos, larvae, and adults that are essentially free of endogenous nuclease and protease activities and appear to be an excellent substrate for investigating chromatin structure inC. elegans. This procedure has enabled us to report the first observations ofC. elegansbasic chromatin structure, as well as characterize HSP16 chromatin structure in detail. The data suggest that differential HSP16 RNA accumulation following 2 hr of heat shock appears to be correlated with a change in the chromatin structure of one of the HSP16 loci to a preinduction, transcriptionally inactive configuratio