Book of Abstracts: Albany 2011
June 14-18 2011
©Adenine Press (2010)
Investigation of Trinucleotide Repeats in Nucleosome Core Particles
Both prokaryotic and eukaryotic genomes have incredible potential to grow, shrink, and change. One such mechanism of change is through the expansion of trinucleotide repeats (TNRs). TNRs occur throughout the genome and their expansion can affect varied cellular processes such as gene expression, mRNA processing, and protein folding. In particular, TNR expansion has been linked to several neurodegenerative diseases, such as Huntington’s Disease, Myotonic Dystrophy (both caused by expansion of CAG•CTG repeats), and Fragile X Mental Retardation (caused by expansion of CGG•CCG repeats) (1). These expansions are ascribed to formation of non-canonical structures in the repeat region, leading to DNA polymerase slippage during replication. DNA repair also appears to play a role in expansion (2).
TNR structure and expansion has been studied both in vivo and in vitro. Work with both oligonucleotides and TNRs incorporated into plasmids indicates the potential to form several stable non-canonical secondary structures (e.g. hairpins) (1). However, genomic DNA is packaged into chromatin. Previous studies have shown that disease-length, expanded CAG•CTG repeats readily incorporate into the basic unit of chromatin packing, the nucleosome core particle (NCP), composed of 146 base pairs of DNA wrapped around a core of eight histone proteins (3). However, long CGG•CCG repeats exclude NCP formation. Here, we seek to investigate the properties associated with shorter repeats (those that have not expanded) incorporated into NCPs. To assess the global interactions involved in interaction between the TNRs and the histone core, we performed competitive nucleosome exchanges to determine the efficiency with which various TNR sequences incorporate into NCPs. It is not yet known what structure TNRs will adopt in this context but understanding that structure is important to understanding how TNRs expand in the genome.
This research has been supported by National Institute of Environmental Health Sciences (NIEHS) award ES019296. C.B.V. is supported by a NDSEG fellowship.
Catherine Burke Volle
Department of Molecular and Cellular Biology and Biochemistry