Vault RNA1-1 riboregulates the autophagic function of p62 by binding to K7/R21 that are critical for p62 oligomerisation

Cellular processes can be regulated at multiple levels, including transcriptional, post-transcriptional and post-translational mechanisms. We have recently shown that the small, non-coding vault RNA1-1 negatively riboregulates p62 oligomerisation in selective autophagy through direct interaction with the autophagic receptor. This function is highly specific for this Pol III transcript, but the determinants of this specificity and a mechanistic explanation of how vault RNA1-1 inhibits p62 oligomerisation are lacking. Here, we combine biochemical and functional experiments to answer these questions. We show that the PB1 domain and adjacent linker region of p62 (aa 1-122) are necessary and sufficient for specific vault RNA1-1 binding, and identify lysine 7 and arginine 21 as key hinges for p62 riboregulation. Chemical structure probing of vault RNA1-1 further reveals a central flexible loop within vault RNA1-1 that is required for the specific interaction with p62. Overall, our data provide molecular insight into how a small RNA riboregulates protein-protein interactions critical to the activation of specific autophagy.