NAA80

NAA80 (NAT6/FUS2) is the dedicated N-terminal acetyltransferase for animal actins, posttranslationally acetylating the processed, acidic N-termini of muscle and non-muscle actin isoforms (β-actin Asp2, γ-actin Glu2, α-actin) and thereby controlling actin filament dynamics and cytoskeletal organization (PMID:29581253, PMID:30028079). Unlike most NATs, its substrate specificity is dictated by acidic residues at positions 2 and 3 of actin rather than positions 1–2, and a crystal structure reveals a NAT-like fold with an unusually open substrate-binding region (PMID:29581307). Acetylation is the terminal maturation event of β-actin (yielding Ac-DDDI-) and prevents N-terminal arginylation (PMID:34896361). Catalysis is enhanced by a stable interaction with profilin 2 (PFN2): NAA80 binds PFN2 through a proline-rich loop, and NAA80, actin, and PFN2 assemble into a ternary complex in which PFN2 boosts intrinsic catalytic activity and promotes acetylation of G-actin before filament incorporation (PMID:32978259). Functionally, loss of NAA80 raises the F/G-actin ratio, increases filopodia and lamellipodia, accelerates cell motility, and fragments the Golgi apparatus in a manner rescued only by catalytically active enzyme (PMID:29581253, PMID:32209306). The enzyme is required in vivo: a homozygous human p.(Leu130Pro) variant reduces actin acetylation and recapitulates the migration and actin phenotypes (PMID:34805998), and zebrafish naa80 knockouts show defective inner ear development and impaired hearing (PMID:39384430).

1. 2000 Medium

   Before any substrate was known, FUS2/NAA80 was established as a cytoplasmic acetyltransferase, framing it as an enzyme in search of a function.

   Evidence sequence homology analysis, in vitro NAT assay with ping-pong kinetics, and GFP-fusion localization

   PMID:10644992

   Open questions at the time

   • Physiological substrate undefined
   • No structural or cellular role established
2. 2018 High

   Identifying actin as the substrate answered what NAA80 does, defining it as the sole NAT for animal actins and linking acetylation to filament dynamics.

   Evidence in vitro acetyltransferase assays, NAA80-knockout human cell lines, reconstituted polymerization/depolymerization, formin elongation and Arp2/3 nucleation assays, and MS validation across independent studies

   PMID:29581253 PMID:30028079

   Open questions at the time

   • Mechanism of cytoskeletal control downstream of acetylation not fully resolved
   • In vivo organismal consequences not yet tested
3. 2018 High

   A crystal structure and yeast complementation explained how NAA80 recognizes its unusual substrate, showing specificity arises from acidic residues at positions 2 and 3 via an open binding cleft.

   Evidence crystal structure of NAA80–bisubstrate inhibitor complex, active-site analysis, and ectopic expression in a NatB-deficient yeast strain

   PMID:29581307

   Open questions at the time

   • No structure of the productive NAA80–actin or ternary complex
   • Determinants of isoform preference not fully mapped
4. 2020 High

   Discovery of PFN2 as a stable partner answered how NAA80 reaches and efficiently acetylates G-actin, defining a profilin-assisted ternary mechanism acting before filament incorporation.

   Evidence interaction proteomics, analytical ultracentrifugation, SAXS, enzyme activity assays, and proline-rich-loop deletion mutagenesis

   PMID:32978259

   Open questions at the time

   • High-resolution structure of the ternary complex lacking
   • Role of other profilin isoforms not addressed
5. 2020 High

   Catalytic-dead rescue established that NAA80 enzymatic activity, not mere presence, maintains Golgi integrity, connecting actin modification state to organelle organization.

   Evidence NAA80 KO cells with wild-type versus catalytic-dead rescue, Golgi immunofluorescence/live imaging, and F-actin quantification

   PMID:32209306

   Open questions at the time

   • Molecular link between actin acetylation and Golgi structure unresolved
   • Effects on Golgi-associated trafficking not measured
6. 2021 High

   Targeted proteomics resolved a competing-modification controversy, establishing NAA80 acetylation as the terminal β-actin maturation state that precludes N-terminal arginylation.

   Evidence NAA80 KO cells with targeted MS-based Nt-modification profiling and antibody comparison

   PMID:34896361

   Open questions at the time

   • Functional consequence of the residual arginylation seen only in KO cells unclear
7. 2021 Medium

   A human homozygous variant demonstrated NAA80's requirement for actin acetylation in vivo and tied loss of function to a human phenotype.

   Evidence patient fibroblasts/PBMCs with p.(Leu130Pro), MS for acetylation, migration and filopodia assays, F-actin quantification, and biochemical stability assessment

   PMID:34805998

   Open questions at the time

   • Single family/variant
   • Genotype–clinical phenotype relationship not fully defined
8. 2024 Medium

   A zebrafish knockout defined an organismal role, showing actin N-terminal acetylation is essential for inner ear development and hearing despite otherwise normal development and muscle.

   Evidence naa80 knockout zebrafish, in vitro acetyltransferase assays, MS, and auditory/morphological phenotyping

   PMID:39384430

   Open questions at the time

   • Cellular mechanism linking acetylation to hair-cell/otolith function unknown
   • Single lab study

• How actin N-terminal acetylation is mechanistically translated into specific filament behaviors, Golgi maintenance, and tissue-specific phenotypes such as hearing remains unresolved.
• No structure of the productive NAA80–actin complex
• Causal chain from acetylation to organelle and sensory phenotypes uncharacterized