Sequence-specific chemical modification of eukaryotic cell chromatin at d(GT)(n) repeats of DNA

DNA and proteins of chromatin from eukaryotic cells were specifically modif ied by an alkylating derivative of pd(AC)(6) (complementary to d(GT) repeat s of DNA) containing a 4-(N-methyl-N-2-chloroethylamino)benzylamine residue on its 5'-end. It was shown that the efficiency of modification of both DN A and proteins increases in the presence of spermine and spermidine and sha rply decreases after preliminary treatment of chromatin by nuclease S1 unde r conditions of mild cleavage of single-stranded DNA reg ions.; It was sugg ested that one of the reasons for the presence of unwound d(GT)(n) stretche s in chromatin DNA accessible for interaction with the complementary oligon ucleotide is the B --> Z transition. Proteins specifically alkylated within the chromatin, which most likely are located in the regions of local unwin ding-of DNA, near the repeats, were analyzed.