Book excerpt: Acidic Proteins of the Nucleus focuses on the functional role of acidic nuclear proteins in differential gene expression. Historically, these proteins are referred to as acidic in nature because they are insoluble in dilute mineral acids and their amino acid composition shows a preponderance of acidic over basic amino acid residues. After an introduction to DNA-binding proteins and transcriptional control in prokaryotic and eukaryotic systems, the subsequent chapters describe various approaches for isolating, separating, and characterizing acidic nuclear proteins. The core chapters specifically cover the isolation, fractionation, and characterization of acidic nuclear phosphoproteins, and the role of these proteins in cell proliferation, cell differentiation, and cell cycle. The last two chapters address the role of acidic nuclear protein in binding steroid hormones and in gene regulation. Each chapter contains some previously unpublished work and provides recommendations for future research. This book will be a good reference background for researchers of acidic nuclear proteins.