Huntingtin (HTT) interactome in regulation of DNA repair/remodeling and RNA processing pathways

Area of Science:

• Neurodegenerative disease research
• Molecular biology
• Genetics

Background:

• Huntington's disease (HD) is a fatal neurodegenerative disorder caused by CAG repeat expansion in the huntingtin (HTT) gene.
• DNA damage response (DDR) pathways are increasingly implicated in HD pathogenesis.
• Understanding HTT's role in DDR is crucial for developing therapeutic strategies.

Purpose of the Study:

• To investigate the interaction of normal and mutant HTT with DDR machinery under genotoxic stress.
• To determine if HD neurons exhibit impaired DSB repair mechanisms.
• To identify novel HTT interactors involved in DNA repair and gene regulation.

Main Methods:

• Utilized multiple biochemical and cellular approaches to analyze HTT interactomes.
• Assessed DNA double-strand break (DSB) repair efficiency in HD and control neurons.
• Investigated the phosphorylation status of HTT (S1181) and its regulation by DNA-PK.
• Performed co-immunoprecipitation assays to identify HTT-interacting proteins.

Main Results:

• HD neurons exhibit impaired DSB repair and increased vulnerability to DSB-induced stress.
• S1181 phosphorylation of HTT is regulated by DSB and mediated by DNA-PK.
• HTT functionally interacts with DNA-PKcs, a key DSB kinase, and localizes to nuclear speckles.
• Identified interactions between HTT, TCERG1, MED15, and the BAF chromatin remodeling complex.

Conclusions:

• HTT plays a significant role in the DSB repair mechanism, potentially acting as a scaffolding protein.
• HTT's interactions with DNA repair factors and chromatin modifiers suggest a role in integrating gene expression and RNA processing during DNA damage response.
• Further research is needed to elucidate the precise physiological outcomes of these HTT interactions in HD pathogenesis.