Investigating acetylation control of MutSbeta protein (Msh2-Msh3) in DNA triplet repeat expansions. (360G-Wellcome-211497_Z_18_Z)

Huntington’s disease (HD) is a debilitating, relentlessly fatal neurodegenerative disease. HD is caused by inheritance of an expanded CAG repeat tract in the HTT gene. The CAG repeat continues expanding in the brain of HD patients, and these somatic expansions contribute to disease progression and age of onset. It is known from model systems that the DNA repair protein MutSbeta (Msh2-Msh3 complex) is essential to drive expansions, as knockout of either Msh2 or Msh3 blocks nearly all expansions. Recent work from the supervisor’s laboratory suggests that MutSbeta expansion activity is regulated by post-translational acetylation. This link to protein acetylation is noteworthy with regard to potential therapy, in light of the supervisor’s recent demonstration that inhibiting histone deacetylase 3 in HD mice blocked disease onset. Using cultured human cells, I will test potential acetylation control of the Msh2 subunit of MutSbeta by mutating a putative acetylation site, lysine 73, to convert it to the non-acetylatable arginine (Msh2K73R). I will then test Msh2K73R protein expression and its ability to form MutSbeta complex. I will assist in genetic assays to measure CAG repeat expansions in cells expressing Msh2K73R, compared to wild type. My prediction is Msh2K73R will drive expansions in an acetylation-independent manner.