Mutant Huntingtin protein (Htt) is predicted to be a major cause of neuronal dysfunction in Huntington’s Disease. A major feature of pathology is the formation of intraneuronal inclusions of Htt protein. Prior work in the Hatters lab has found that soluble mutant Huntingtin exon 1 fragment elicits a strong apoptotic response in cultured cells and that the trigger for apoptosis wanes when Htt aggregates into inclusions. We hypothesize that newly synthesized mutant Htt is recognized as abnormal by ribosome-associated quality control mechanisms and when this system is overwhelmed it triggers apoptosis. In this project we are building a suite of new molecular biology tools to capture the interactors of newly synthesized mutant Htt exon 1 in order to identify the components mediating the ribosome-associated quality control mechanisms. To capture and identify interactors we combined a proximity labeling method called TurboID with an epitope targeting approach called SunTag. The gist is that TurboID can target a biotin ligase to an epitope attached to the mutant Htt so we can define the interactors. We have tested this new strategy on model system lamin, which is a component of nuclear envelope and found that biotin ligase can specifically label biotin within 30 min to the cells. For further evaluation, we will compare proteins identified by this new strategy and known lamin interactors. Next, to target newly synthesized Htt, we are now working to blend another tool into this system called TimeStamp, which involves a protease to self-cleave an epitope that can be regulated in activity with a drug. The ultimate goal is to use TimeStamp to cleave off the SunTag epitope from older proteins so that we can restrict the biotinylation process to just the newly synthesized proteins.