Comparative studies on chromatin proteins from chicken thrombocytes and erythrocytes

Comparative studies on chromatin composition, nature of non-histone chromatin proteins, histone fractions and the activity of chromatin-bound protease from chicken thrombocytes and erythrocytes were performed. Chemical analysis of chromatin preparations indicated the lack of an essential difference in the protein/DNA ratio. Analysis of non-histone chromatin proteins in SDS-polyacrylamide gel electrophoresis and isoelectric focusing showed a striking similarity of their electrophoretic patterns. Quantitative rather than qualitative differences predominated. During acidic urea-polyacrylamide gel electrophoresis, it was found that histones from thrombocytes contain a fraction migrating with the electrophoretic mobility of histone H5 from erythrocytes. This fraction constitutes 6.7% and 19% of total histone in thrombocytes and erythrocytes, respectively. The electrophoretic patterns of histones, as well as the amount of peptides soluble in 25% trichloroacetic acid released during incubation of chromatin and isolated histones at pH 8, indicated that the activity of chromatin-bound protease was significantly higher in thrombocytes than in erythrocytes.