1. Chicken liver nuclei were fractionated by disruption with ultrasound and subsequent precipitation with divatent cations. A small, protein-rich fraction (CS), representing less than 5% of the total nuclear DNA reacted strongly with antisera to dehistonized chicken liver chromatin. 2. Further fractionation of the CS by DNA-affinity chromatography yielded two DNA-binding immunoreactive proteins (approximate Mr 35 and 56 kD). 3. We have shown previously (Kiliańska et al., 1981, Kiliańska, 1984) that this DNA-binding component strongly inhibited the in vitro transcription of RNA.
