Purification of a low molecular weight non-histone chromosomal protein.

A non-histone chromosomal proteins was extracted from rat liver chromatin with 0.35 M NaCl and purified more than 2758 times to near homogeneity by hydroxyapatite, gel filtration, and phosphocellulose chromatography. The final fraction was greater than 95% pure as judged by non-denaturing gel electrophoresis. The protein, designated loosely bound non-histone chromosomal protein 1, had an observed molecular weight of 15 700. This protein was demonstrated to increase the amount of RNA synthesized in a heterologous (Escherichia coli RNA polymerase) transcription system and, therefore, this activity was also used to monitor its purification. The availability of highly purified loosely bound non-histone chromosomal protein 1 will make possible an examination of its structural and/or functional role in chromatin.