PREFERENTIAL NUCLEOSOME ASSEMBLY AT DNA TRIPLET REPEATS FROM THE MYOTONIC-DYSTROPHY GENE

The expansion of CTG repeats in DNA occurs in or near genes involved i n several human diseases, including myotonic dystrophy and Huntington' s disease. Nucleosomes, the basic structural element of chromosomes, c onsist of 146 base pairs of DNA coiled about an octamer of histone pro teins and mediate general transcriptional repression. Electron microsc opy was used to examine in vitro the nucleosome assembly of DNA contai ning repeating CTG triplets. The efficiency of nucleosome formation in creased with expanded triplet blocks, suggesting that such blocks may repress transcription through the creation of stable nucleosomes.