ABSTRACT
This chapter provides a general overview of the nonhistone nuclear phosphoproteins and some information on the structure of nonhistone phosphoproteins. In general, the presumption of chromatin association of most of the nonhistone phosphoproteins is still valid, although many of the nuclear nonhistone proteins have been shown to be present in regions of the nucleus which cannot strictly be considered as chromatin. Once a protein or protein fraction is identified as phosphorylated, an attempt may be made to quantitate the degree of phosphorylation. If nonhistone phosphoproteins regulate transcription of specific genes they would be expected to recognize and bind to specific sites on DNA. Various hormones and chemical agents which stimulate transcription have been used to correlate changes in nonhistone phosphoproteins with changes in gene activities. The high mobility group of proteins is a subclass of nonhistone proteins defined by their extractability from chromatin by 0.35 M NaCl, their solubility in 2% trichloroacetic acid, and their relatively high electrophoretic mobility.
