Role of Nonhistone Chromosomal Proteins in Selective Gene Expression
It is becoming increasingly apparent that chromosomal proteins — histones and nonhistone chromosomal proteins — play an important role in dictating structural and functional properties of the eukaryotic genome. Components of the nonhistone chromosomal proteins may also be involved in the maintenance of genome structure. Nonhistone chromosomal proteins are synthesized in the cytoplasm. Nonhistone chromosomal proteins can undergo several types of postsynthetic modification. Glycoproteins have been found in the nonhistone chromosomal proteins of sea urchin. Phospholipids have been found to be attached to nonhistone chromosomal proteins from brain and lymphocytes. The kinase activity responsible for phosphorylating the nonhistone chromosomal proteins is located in the chromatin. Some nonhistone chromosomal proteins are difficult to isolate because of their tight binding to DNA and their tendency to aggregate with each other and with histones. Due to the complex and heterogeneous nature of the nonhistone chromosomal proteins, fractionation is a prerequisite for examination of the chemical, metabolic, and biological properties of the individual proteins.