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J Biol Chem. 2019 Mar 6. pii: jbc.RA118.007204. doi: 10.1074/jbc.RA118.007204. [Epub ahead of print]

Design and characterization of mutant and wild-type huntingtin proteins produced from a toolkit of scalable eukaryotic expression systems.

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Structural Genomics Consortium, University of Toronto, Canada.
Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Canada.
Custom Biologics, Canada.
Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in Saint Louis, United States.
Basic Science Program, SAXS Core facility of National Cancer Institute, Frederick National Laboratory for Cancer Research, United States.
Tau Consortium, United States.
Structural Genomics Consortium and Princess Margaret Cancer Centre, University of Toronto, Canada.


The gene mutated in individuals with Huntington's disease (HD) encodes the 348-kDa huntingtin (HTT) protein. Pathogenic HD CAG-expansion mutations create a polyglutamine (polyQ) tract at the N terminus of HTT that expands above a critical threshold of ~35 glutamine residues. The effect of these HD mutations on HTT is not well understood, in part because it is difficult to carry out biochemical, biophysical, and structural studies of this large protein. To facilitate such studies, here we have generated expression constructs for the scalable production of HTT in multiple eukaryotic expression systems. Our set of HTT expression clones comprised both N- and C-terminally FLAG-tagged HTT constructs with polyQ lengths representative of the general population, HD patients, and juvenile HD patients, as well as the more extreme polyQ expansions used in some HD tissue and animal models. Our expression system yielded milligram quantities of pure recombinant HTT protein, including many of the previously mapped posttranslational modifications. We characterized both apo and HTT-HTT-associated protein 40 (HAP40) complex samples produced with this HD resource, demonstrating that this toolkit can be used to generate physiologically meaningful HTT complexes. We further demonstrate that these resources can produce sufficient material for protein-intensive experiments, such as small-angle X-ray scattering (SAXS), providing biochemical insight into full-length HTT protein structure. The work outlined and the tools generated here lay a foundation for further biochemical and structural work on the HTT protein and for studying its functional interactions with other biomolecules.


Huntington disease; biophysics; molecular dynamics; neurodegeneration; protein expression; protein purification; small-angle X-ray scattering (SAXS)

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