CUL4A-DDB1-DCAF10 is an N-recognin for N-terminally acetylated Src kinases

Co-translational N-terminal modifications such as methionine excision, acetylation, and myristoylation contribute to protein stability, localization, and folding (1). Disrupting these modifications exposes short N-terminal degron motifs that trigger protein degradation via the ubiquitin-proteasome system, safeguarding the proteome (2). While N-terminal acetylation typically protects proteins, it may also promote degradation through the Ac/N-degron pathway (3). Src family kinases (SFKs), key regulators of signaling and tumorigenesis, require N-terminal myristoylation for functon(4). Using peptide pull-downs, mass spectrometry, and AlphaFold 3 predictions, we identified the E3 ligase adaptor DCAF10 as a receptor for aberrantly N-terminally acetylated SFKs. SiRNA knockdowns confirmed that DCAF10 regulates SFK levels, with acetylated glycine as the key recognition signal. In vitro, a CUL4A-DDB1-DCAF10 complex recapitulated ubiquitination of N-terminally acetylated Lyn. Thus, our results uncover a novel N-degron pathway that monitors myristoylation replacement with acetylation and activates degradation of SFKs in presence of the latter. This mechanism may protect other, and potentially all, N-terminally myristoylated proteins.