The localization and interactions of huntingtin.

Huntingtin was localized by using a series of antibodies that detected different areas of the protein from the immediate N-terminus to the C-terminal region of the protein. The more C-terminal antibodies gave a cytoplasmic localization in neurons of the brain in controls and cases of Huntington's disease (HD). The N-terminal antibody, however, gave a distinctive pattern of immunoreactivity in the HD brain, with marked staining of axon tracts and white matter and the detection of densely staining intranuclear inclusions. This implies some processing differences between mutated and normal huntingtin. We have also localized two interacting proteins, cystathionine beta-synthase and the nuclear receptor co-repressor (N-CoR), in brain. Cystathionine beta-synthase was not relocalized in HD brain, but the N-CoR was excluded from neuronal nuclei in HD brain, and a further protein that exists in the same repression complex, mSin3, was similarly excluded. We conclude that the co-repressor might have a part in HD pathology.