Molecular architecture and assembly of the human RNA Degradosome

The PNPase exoribonuclease interacts with the SUV3 helicase to form the human RNA Degradosome responsible for processive mitochondrial RNA turnover and quality control. Although structural data reveals the trimeric PNPase architecture along with the monomeric and dimeric states of SUV3, the molecular basis of their assembly for processive RNA degradation remains poorly understood. Here we present the molecular characterization of the human RNA Degradosome and define critical molecular features that regulate complex formation. We identify the protein regions required for RNA Degradosome formation and establish the minimum components necessary for the SUV3-PNPase interaction. Chemical crosslinking mass spectrometry analysis reveals distance restraints that position the SUV3 N-terminal domain alongside of the PNPase S1 domain, defining an important interface for complex formation. These findings provide mechanistic insight into how PNPase and SUV3 assemble to form the human RNA Degradosome.