TGME49_212820

The Toxoplasma gondii ubiquitin family protein DSK2 (TGGT1_223680) is a UBL-UBA shuttle protein that, together with DDI1 and RAD23, escorts ubiquitinylated proteins to the proteasome for degradation (PMID:32808330). It localizes to both the cytoplasm and the nucleus, and combined deletion of these shuttle factors causes accumulation of ubiquitinylated proteins and asynchronous parasite cell division, linking DSK2-dependent proteasomal targeting to synchronous division (PMID:32808330). Beyond (PMID:32808330), no further mechanistic detail — including substrate specificity, direct proteasome contacts, or the individual contribution of DSK2 relative to DDI1 and RAD23 — has been characterized in the available corpus.

1. 2020 Medium

   It was unknown whether Toxoplasma encodes UBL-UBA shuttle proteins linking ubiquitinylation to proteasomal degradation; knockout showed DSK2 (with DDI1 and RAD23) is required to clear ubiquitinylated proteins and maintain synchronous division, establishing a shuttle-to-proteasome role tied to cell-cycle fidelity.

   Evidence Triple-gene deletion, imaging-based localization, and assays of ubiquitinylated-protein accumulation and cell-division phenotype in T. gondii GT1

   PMID:32808330

   Open questions at the time

   • The individual contribution of DSK2 versus DDI1 and RAD23 is not resolved by the combined deletion
   • No specific ubiquitinylated substrates or direct proteasome contacts were identified
   • The mechanistic link between shuttle-protein loss and asynchronous division was not defined

• The substrate repertoire, binding partners at the proteasome, and the mechanism by which DSK2 loss disrupts division synchrony remain undefined.
• No substrate identified for DSK2
• No structural or biochemical characterization of UBL/UBA-mediated proteasome docking
• DSK2-specific phenotype uncoupled from DDI1/RAD23 not established