bioPROTACs as versatile modulators of intracellular therapeutic targets including proliferating cell nuclear antigen (PCNA)

Proc Natl Acad Sci U S A. 2020 Mar 17;117(11):5791-5800. doi: 10.1073/pnas.1920251117. Epub 2020 Mar 2.


Targeted degradation approaches such as proteolysis targeting chimeras (PROTACs) offer new ways to address disease through tackling challenging targets and with greater potency, efficacy, and specificity over traditional approaches. However, identification of high-affinity ligands to serve as PROTAC starting points remains challenging. As a complementary approach, we describe a class of molecules termed biological PROTACs (bioPROTACs)-engineered intracellular proteins consisting of a target-binding domain directly fused to an E3 ubiquitin ligase. Using GFP-tagged proteins as model substrates, we show that there is considerable flexibility in both the choice of substrate binders (binding positions, scaffold-class) and the E3 ligases. We then identified a highly effective bioPROTAC against an oncology target, proliferating cell nuclear antigen (PCNA) to elicit rapid and robust PCNA degradation and associated effects on DNA synthesis and cell cycle progression. Overall, bioPROTACs are powerful tools for interrogating degradation approaches, target biology, and potentially for making therapeutic impacts.

Keywords: PCNA; bioPROTAC; targeted degradation.

MeSH terms

  • Binding Sites
  • HEK293 Cells
  • Humans
  • Molecular Targeted Therapy / methods
  • Proliferating Cell Nuclear Antigen / chemistry
  • Proliferating Cell Nuclear Antigen / metabolism*
  • Protein Binding
  • Protein Engineering / methods*
  • Proteolysis*
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Ubiquitin-Protein Ligases / chemistry
  • Ubiquitin-Protein Ligases / genetics*
  • Ubiquitin-Protein Ligases / metabolism


  • Proliferating Cell Nuclear Antigen
  • Recombinant Proteins
  • Ubiquitin-Protein Ligases