Investigating The Role Of Histone Modification In Nucleosome Formation By Cag/Ctg Repeats

Huntington's Disease is a neurodegenerative disorder caused by the expansion of CAG/CTG trinucleotide repeats within exon 1 of the huntingtin gene. Previous research has demonstrated that the longer the repeat tract, the greater likelihood that CAG/CTG repeats will be incorporated into the nucleosome, the most basic unit of DNA packaging in the genome. The histone proteins that form those nucleosomes in the cell have many epigenetic markers that can alter the packaging of the nucleosome. Additionally, these modifications may change the affinity of the DNA for the histone core. Interestingly, while the interaction of CAG/CTG repeat DNA with histone proteins has been extensively studied as a function of repeat length, there is yet to be a study that investigates the effect of the histones and their epigenetic marks on nucleosome formation by CAG/CTG repeats. Here, we express and purify histones from a recombinant source and use them to form nucleosomes in a nucleosome incorporation assay. We can then compare the formation of nucleosomes with the recombinant histones to nucleosomes formed with histones isolated from chicken erythrocytes, thus elucidating the general effect of histone modification on nucleosome formation by CAG/CTG repeats.