Dimerization-dependent serine protease activity of FAM111A prevents replication fork stalling at topoisomerase 1 cleavage complexes.

Publication Type:

Journal Article


Nat Commun, Volume 15, Issue 1, p.2064 (2024)


Dimerization, DNA Replication, Proteolysis, Serine, Serine Endopeptidases, Serine Proteases


<p>FAM111A, a serine protease, plays roles in DNA replication and antiviral defense. Missense mutations in the catalytic domain cause hyper-autocleavage and are associated with genetic disorders with developmental defects. Despite the enzyme&#39;s biological significance, the molecular architecture of the FAM111A serine protease domain (SPD) is unknown. Here, we show that FAM111A is a dimerization-dependent protease containing a narrow, recessed active site that cleaves substrates with a chymotrypsin-like specificity. X-ray crystal structures and mutagenesis studies reveal that FAM111A dimerizes via the N-terminal helix within the SPD. This dimerization induces an activation cascade from the dimerization sensor loop to the oxyanion hole through disorder-to-order transitions. Dimerization is essential for proteolytic activity in vitro and for facilitating DNA replication at DNA-protein crosslink obstacles in cells, while it is dispensable for autocleavage. These findings underscore the role of dimerization in FAM111A&#39;s function and highlight the distinction in its dimerization dependency between substrate cleavage and autocleavage.</p>

8S9K (SPD S541A) and 8S9L (mini-SPD)
8S8K, Structure of dimeric FAM111A SPD S541A Mutant