Abstract
Native chromatin [rat liver nuclei] and chromatin subunits (nucleosomes) were titrated with polylysine and digested with micrococcal nuclease and DNase I at individual lysine/nucleotide ratios. In contrast to using mechanically sheared chromatin, a comparison of the sites accessible for micrococcal nuclease and polylysine reveals that polylysine does not preferentially protect the micrococcal-nuclease-susceptible sites in chromatin. Similar results were obtained in digestion with DNase I. Polylysine apparently does not preferentially bind to the internucleosomal DNA, which is the prime target site for micrococcal nuclease, but rather to the total nucleosomal DNA moiety.