Effects of basic nuclear proteins on cardiac muscle function.

• Recent data obtained in this laboratory suggest that basic nuclear proteins may exert some controlling extranuclear influence on cellular activity. For example, very low concentrations of purified histones obtained from thymus, liver, kidney and brain, as well as semipurified histones derived from heart and skeletal muscle, inhibit a membraneATPase system associated with active cation transport, stimulate a Mg-dependent mitochondrial ATPase' and inhibit ATPases and syneresis of actomyosin and myofibrillar suspensions. These effects were particularly evident when histones prepared from cardiac muscle nuclei were reacted with the subcellular components from the same muscle. The role of the nucleus or nuclear proteins in cardiac muscle function has received very little attention. In fact, it is only recently that some studies have been directed towards RNA and DNA metabolism in cardiac hypertrophy." Other than a brief reference to the presence of histones or basic nuclear proteins in cardiac muscle, no data on heart histones have been reported. The basic nuclear proteins are thought to be associated with gene expression. According to this theory a histone-DNA binding results in "selective"