Function and Molecular Mechanism of N-Terminal Acetylation in Autophagy

Acetyl (Ac-) ligation to the amino acids in a protein is an important post-translational modification to regulate protein functions. However, in contrast to lysine acetylation, the N-terminal acetylation is elusive for its cellular functions.  Here, we identified Nat3 as an N-terminal acetyltransferase essential for autophagy, a catabolic pathway for bulk transport and degradation of cytoplasmic components. We identified the actin cytoskeleton constituent Act1 and dynamin-like GTPase Vps1 as substrates for Nat3 mediated N-terminal acetylation on the first methionine. Specifically, acetylated Act1 forms actin filaments and therefore promotes the transport of Atg9 vesicles for autophagosome formation; acetylated Vps1 recruits and facilitates bundling of SNARE complex for autophagosome fusion with vacuoles. Abolishment of the N-terminal acetylation of Act1 and Vps1 is associated with blockage of upstream and downstream steps of autophagy process respectively. Therefore, our work shows the first that protein N-terminal acetylation plays a critical and ancient role in controlling of autophagy by finetuning multiple steps of this process.