Histones in Chick Embryonic Erythropoiesis

Abstract

Changes in histones from erythroid cells of the developing chick were examined. Basic proteins extracted from erythroid nuclei from embryos 2½ to 19 days old, from newly hatched chicks, and from adult chicks were characterized by acrylamide gel electrophoresis. The same histone components are present throughout this period of development with only minor quantitative differences, except that histone V increases from a very low value to 13.5% of all histones by Day 19 of incubation and to 21% in the adult. Histone V (f2c) has been described by others as unique to nucleated red cells. No other histone component was apparently replaced by the new histone V. The increase of histone V corresponds in time to the transition from the primitive to the definitive erythroid cell line in the chick embryo and also to the terminal division of the primitive erythroid cells. Pulse-chase experiments in 5-day primitive erythroblasts with radioactive amino acids showed that histone V, and to a lesser extent histone III, were the most rapidly synthesized histones. A 2-hour chase showed these histones to be the final, stable protein product. This active synthesis of histone V appears to be temporally coordinated with the last cell division of the primitive series.