Changes of chromatin structure induced by acid mucopolysaccharides

Abstract

1. 1. Rat liver chromatin was treated in vitro with several types of acid mucopolysaccharide, such as heparin, chondroitin sulfates (A, B and C), and hyaluronic acid. The induced change in chromatin was examined by two assay methods—measurement of the susceptibility to DNase, and of the kinetics of dye-binding. 2. 2. DNA in native chromatin was degraded by pancreatic DNase I much slower than protein-free DNA. However, the degradation of chromatin DNA was accelerated to various degrees in the presence of acid mucopolysaccharides: most conspicuously by heparin, to a lesser extent by chondroitin sulfates (A, B and C), and not at all by hyaluronic acid. In the presence of an appropriate amount of heparin, chromatin was observed to be degraded as rapidly as protein-free DNA. 3. 3. The number of available binding sites in chromatin for ethidium bromide (EB) was determined by titration and plotting according to Scatchard. Approximately one-half of the binding sites were available in native chromatin as compared with protein-free DNA. Treatment with an appropriate amount of heparin made practically all binding sites in the chromatin available for the dye. A less marked effect was observed with chondroitin sulfate B, but practically no effect was seen with chondroitin sulfate A, C or hyaluronic acid. 4. 4. The data obtained by using acridine orange agreed well with those found with EB.