Some properties of polylysine-accessible DNA.

DNA regions in rat liver chromatin which are accessible to polylysine were isolated using three molecular weights of polylysine so as to overcome possible artefacts in measuring the DNA size. Sucrose gradient centrifugation showed a series of peaks or shoulders corresponding to sizes of 65, 110, 210, 370, 600 and 1,200 base pairs. Accessible DNA was enriched in and co-sedimented with rapidly synthesized RNA but the RNA was digestible by RNAase A, indicating that most of each RNA molecule was single-stranded (possibly hybridised to DNA at one end). The reassociation rate of accessible DNA was similar to that of whole DNA up to about Cot 50, but was slower at higher cost values.