Cotranslational modification by N-terminal acetylation occurs when N-terminal acetyltransferases (NATs) modify nascent polypeptides as they emerge from the ribosome. Thomas Arnesen at the University of Bergen has reviewed how this modification is widespread in eukaryotes, affecting the majority of human proteins and establishing it as a fundamental determinant of the nascent proteome. The modification is enzyme- and sequence-specific, so effects vary by substrate and cellular context.
Mechanisms linking acetylation to stability
At the molecular level, N-terminal acetylation alters the chemical properties of the protein N-terminus. In some cases the acetyl group blocks a free alpha-amino group, preventing pathways that require an unmodified N-terminus to trigger degradation. Conversely, acetylation can also create a specific recognition signal called an Ac/N-degron, a concept developed by Alexander Varshavsky at Caltech. Ac/N-degrons are bound by specific E3 ubiquitin ligases that mark the protein for ubiquitination and subsequent proteasomal degradation. Thus, the same modification can either protect a protein from turnover or actively target it for removal depending on sequence context, compartmental localization, and the complement of quality-control factors present.
Consequences for cellular biology and disease
The net effect on protein half-life influences cellular homeostasis: stability controls stoichiometry in multiprotein complexes, regulates signaling durations, and enforces removal of misfolded or surplus polypeptides. Subtle shifts in acetyltransferase activity or in ligase recognition can therefore ripple into large proteome changes. Clinically, perturbations of NAT function have been linked to developmental and neurological phenotypes in humans, illustrating how cotranslational acetylation contributes to organismal physiology beyond single-protein effects.
Because NATs are co-translational, the effect of N-terminal acetylation is tied to translation dynamics, chaperone engagement, and subcellular targeting, producing tissue- and species-specific outcomes. Environment and lifestyle that affect translation rates or proteostasis capacity can modulate how acetylation influences stability. From a translational perspective, understanding which proteins are stabilized or degraded by Nt-acetylation points to strategies for therapeutic modulation of proteostasis in disease states, a research direction motivated by foundational studies from Arnesen at the University of Bergen and Varshavsky at Caltech. Precise outcomes remain substrate-dependent, making experimental context essential for interpretation.