Characteristics of nuclear proteins during granulocyte development.

Alterations in nuclear proteins during maturation may be responsible for gene activation and repression. Study of these proteins requires: (1) a system for separating cells into varying degrees of maturity, and (2) a procedure for separating the nuclear proteins. The former was accomplished using Ficoll/Hypaque density gradients to separate rabbit granulocyte precursors. Erythrocytes and their precursors were removed by hypotonic lysis. Histones were extracted from purified nuclei with sulfuric acid, and analyzed on polyacrylamide gels containing urea. Residual non-histone proteins were separated by electrophoresis on sodium dodecyl sulfate-polyacrylamide gels. Quantitation of nuclear proteins during development shows no change in the histones, but a significant increase in the non-histone proteins. Therefore, the ratio of non-histone to histones increases progressively during maturation. Histone electrophoresis revealed no significant qualitative or quantitative changes in their five major classes during development. By contrast, electrophoretic analysis of the non-histone proteins revealed distinct changes which include a striking decrease in low molecular weight protein during maturation, and also certain changes in other peptide bands. These changes may reflect alterations in nuclear structure, a changing complement of the nuclear proteins involved in genetic regulation, or a combination of both.