Nucleosome repeat lengths in the definitive erythroid series of the adult chicken.

Morris [1] has suggested that the difference in nucleosome repeat length between chicken liver (200 base pairs) and mature chicken erythrocytes (212 base pairs) may be due to the presence of histone H5 which is found in chicken erythroid cells but not in other tissues. Levels of H5 increase during erythroid maturation in the adult chicken. To determine what influence H5 might have on repeat length, erythroid populations at various stages of maturation were isolated, and repeat lengths and levels of H5 were determined. Bone marrow cells from anemic chickens were cultured in vitro to permit non-cycling erythroblasts to mature and thus increase in density. Less dense cycling basophilic erythroblasts were then isolated by buoyant density centrifugation. This erythroblasts were then isolated by buoyant density centrifugation. This population has a repeat length of 205 base pairs and an H5 content roughly two-thirds that of mature erythrocytes, which have a repeat length of 212 base pairs. A population intermediate in maturation, consisting of cells of the anemic pheripheral blood, has a repeat length of 218 base pairs, and the predominant cell type in this population has an H5 content greater than that of mature erythrocytes. Therefore, changes in histone H5 content are reflected by the nucleosome repeat length during erythroid maturation.