Eukaryotic cells contains thousands of different proteins, many of which are required for only brief periods during the cellular cycle. These short-lived proteins, along with any misfolded or damaged intracellular proteins, are destroyed by a large proteolytic complex named the 26S proteasome.... read more

In E. coli, CRISPR transcripts are processed into short RNAs that are incorporated into a large ribonucleoprotein surveillance complex called Cascade. This complex specifically targets and binds foreign nucleic acids in a sequence-specific manner, followed by degradation of the targeted substrate. We used cryo-electron microscopy to determine the structure of Cascade before and after binding to a target substrate... read more

The eukaryotic exosome is a conserved complex important for 3' end trimming and degradation of RNA. In yeast, the Rrp44 protein constitutively associates with the nine-subunit core exosome and provides the sole sources of processive 3'-to-5' exoribonuclease activity. We have obtained EM reconstructions of the core and Rrp44-bound exosome complexes... read more