Comparison of some properties of chromatin non-histone proteins and nuclear sap proteins

The in vivo disposition of aflatoxin B1 in rat liver

The disposition of a non-toxic i.p. dose of [3H]-aflatoxin B1 (0.70 micrograms/kg) in the blood, plasma, and liver was studied in male Wistar rats. Uptake into the blood, plasma, and liver was biphasic; there was an initial rapid rise (0-2 hr) followed by a second phase (2-12 hr) of a gradual increase. Most of the radioactivity in the blood was bound noncovalently to albumin. Distribution of radioactivity in the subcellular fractions of liver showed that the microsomes exhibited the highest labeling which increased over the time course; labeling of the cytosol reached a maximum at 2 hr then decreased to a new steady state, whereas the mitochondria and nuclei reached a plateau. When the content of aflatoxin B1 in the nuclear subfractions was examined, greater than 92% of the total radioactivity was found in the deoxyribonucleoprotein fraction, and 84% of this was bound noncovalently. These results suggest that aflatoxin B1 is transported from the site of injection through the blood to the liver and its subcellular and subnuclear fractions primarily in a noncovalent form.

The effect of gamma-radiation on the interaction of DNA with nuclear non-histone proteins

The interaction of nuclear sap proteins and chromatin non-histone proteins with DNA was studied by two methods: membrane filter technique and chromatography of 32P-labelled proteins on DNA-containing columns. Irradiated DNA binds a slightly greater amount of these proteins and much more firmly than the native DNA. The effect is caused by the appearance of the locally denatured sites in irradiated DNA. Irradiation of non-histone proteins disturbs their specific interaction with DNA more easily than the non-specific binding.