C646 degrades Exportin-1 to modulate p300 chromatin occupancy and function

Area of Science:

• Biochemistry
• Molecular Biology
• Epigenetics

Background:

• Molecular glues induce protein degradation by linking target proteins to ubiquitin ligases.
• Discovery strategies for molecular glues are limited.
• C646 is known to inhibit histone acetyltransferase p300.

Purpose of the Study:

• To identify novel molecular glues and their targets.
• To investigate the mechanism of C646-induced cytotoxicity.
• To explore the role of Exportin-1 (XPO1) in C646's action.

Main Methods:

• Screening of 3,200 bioactive small molecules.
• Utilizing neddylation-dependent protein degradation assays.
• Employing drug-resistance alleles (XPO1^C528S) to validate target specificity.
• Chromatin immunoprecipitation to assess protein occupancy.

Main Results:

• C646 induces cytotoxicity via neddylation-dependent protein degradation.
• C646 directly targets and degrades Exportin-1 (XPO1), not p300.
• Cellular phenotypes induced by C646 are reversed by the XPO1^C528S resistance allele.
• C646 and XPO1 modulator S109 reduce chromatin occupancy of both XPO1 and p300.

Conclusions:

• C646 acts as a molecular glue targeting XPO1 for degradation.
• XPO1 plays a role in regulating chromatin state, alongside p300.
• XPO1 is a validated target for modulating chromatin and cellular processes.