An RNA–protein complex regulates gene expression in an unanticipated way.
The cellular machines called spliceosomes reconfigure transcribed RNA into its mature, protein-coding form. The 'minor spliceosome' is less than 1% as abundant as the major spliceosome, but exists in plants, fungi and animals, with precursors to hundreds of human messenger RNAs containing a section removed only by the minor spliceosome. Researchers led by Gideon Dreyfuss at the University of Pennsylvania School of Medicine in Philadelphia showed that a component of the minor spliceosome, an RNA–protein complex called U6atac, is extremely unstable and normally limits the machine's activity. When cells are stressed, however, signalling enzymes stabilize U6atac, boosting its levels and increasing the production of mature RNAs. This allows the minor spliceosome to perform as a quick-acting valve to switch on the production of certain proteins.