The Effect of the Simple Repeating d(CG.GC) n,d(CA.GT) n,and d(A.T) n DNA Sequences on the Nucleosomal Organization of SV40 Minichromosomes

The effect of several simple repeating DNA sequences—d(CG.GC)₅, d(CA.GT)₃₀, and d(A.T)₆₀—on the nucleosomal organization of the SV40 minichromosome is analyzed. These three different sequences were cloned at the Hpa II site of SV40 (position 346) which occurs at the 3′ border of the nucleosome-free SV40 control region. Our results show that neither the d(A.T)60 sequence nor the d(CG.GC)5 sequence appear to have any relevant effect on the nucleosomal organization of the region of the minichromosome surrounding the inserted repeated sequence. Both sequences are hypersensitive to micrococcal nuclease cleavage in the minichromosome, indicating that they are not organized into nucleosomes. On the other hand, the d(CA.GT)30 sequence is found organized as nucleosomes and causes the delocation of nucleosomes in the minichromosomal region close to the inserted repeated sequence.