Development of PolyHis-Targeting PROTAC Degraders

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Biology

Background:

• Targeted protein degradation (TPD) utilizes proteolysis targeting chimeras (PROTACs) to eliminate proteins of interest (POIs) through the ubiquitin-proteasome system (UPS).
• A major limitation for PROTAC application is the scarcity of high-quality target ligands for many proteins, hindering the assessment of their degradability.
• Existing tag-based systems for protein degradation have limitations that restrict their broad applicability.

Purpose of the Study:

• To develop a versatile platform for targeted protein degradation independent of specific target ligands.
• To overcome the limitations of current tag-based degrader systems.
• To enable the assessment of protein degradability for previously undruggable targets.

Main Methods:

• Development of polyhistidine-targeting PROTACs (polyHisTACs) by linking a Ni²⁺-NTA headgroup to VHL or CRBN E3 ligase ligands.
• Recruitment of E3 ligase complexes to polyhistidine-tagged proteins of interest (POIs).
• Degradation assays using CRISPR-engineered, endogenously polyHis-tagged BRD4 and exogenously expressed, polyHis-tagged PSPC1.

Main Results:

• PolyHisTACs successfully degraded CRISPR-engineered, endogenously polyHis-tagged BRD4.
• Robust degradation of an exogenously expressed, polyHis-tagged RNA-binding protein, PSPC1, was achieved.
• The polyHisTAC system demonstrated effectiveness even for a typically undruggable target.

Conclusions:

• PolyHisTACs provide a versatile and reliable method for evaluating UPS-mediated degradability without requiring target-specific ligands.
• This platform facilitates acute protein of interest (POI) depletion in basic research settings.
• The minimal and easily implemented polyhistidine tag overcomes key limitations of existing tag-based degrader systems.