Ascorbate peroxidase (APEX2) -mediated proximity-based proteomics for HTT protein interactions

Huntington’s Disease (HD), a progressive neurodegenerative disorder with no disease-modifying therapies, is caused by a CAG repeat expansion in the HD gene encoding polyglutamine-expanded huntingtin (HTT) protein. Mechanisms of HD cellular pathogenesis and cellular functions of the normal and mutant HTT proteins are still not completely understood. HTT protein has numerous interaction partners, and it likely provides a scaffold for assembly of multiprotein complexes many of which may be altered in HD. Previous studies have implicated DNA damage response in HD pathogenesis. Gene transcription and RNA processing has also emerged as molecular mechanisms associated with HD. Here we used multiple approaches to identify HTT interactors in the context of DNA damage stress. We present evidence for the role for HTT in double strand break (DSB) repair mechanism. Our results indicate that HTT interacts with many proteins involved in the regulation of interconnected DNA repair/remodeling and RNA processing pathways.