Rohner et al. describe how the heat shock gene hsp-16.2 associates with nuclear pore complexes in C. elegans cells.
Genes can occupy specific positions within the nucleus, and their localization may change upon activation or repression. Developmentally regulated genes in C. elegans, for example, move from the periphery to the interior of nuclei in response to gene induction. In contrast, Rohner et al. found that the worm stress response gene hsp-16.2 tended to localize near the nuclear envelope in its inactive state and became even more enriched at the nuclear periphery when induced by heat shock.
Transgenes containing the minimal hsp-16.2 promoter showed similar localization patterns, indicating that the promoter region, rather than any other sequences or the gene’s chromosomal location, controls hsp-16.2 positioning. Using super-resolution microscopy and chromatin immunoprecipitation, the researchers found that the promoter localized near nuclear pore complexes before gene induction and then increased its association with the pores upon heat shock.
hsp-16.2’s association with nuclear pores was mediated by several factors that bind to the gene’s promoter. Knocking down heat shock transcription factor 1 or expressing heat-sensitive mutants of RNA polymerase II abolished the gene’s peripheral localization. hsp-16.2 positioning also required the polymerase-associated protein ENY-2, which binds to nuclear pores and promotes mRNA processing and export. hsp-16.2’s peripheral localization may therefore speed up heat shock protein production in times of stress. But senior author Susan Gasser thinks that, in the uninduced state, pore-associated factors might help limit gene expression by promoting mRNA turnover.
Text by Ben Short