ABSTRACT
Proteolysis of histones H1b and H1(0) is observed after the incubation of rat spleen nuclei at 37 degrees C during 1 hour. Adenosine triphosphate, inorganic pyrophosphate and nicotinamide adenine dinucleotide decrease the digestion of histone H1b. ATP, PP1 and NAD+, in the case of 3 hours incubation, do not affect proteolysis of H1 histones in rat spleen nuclei. The incubation of rat liver nuclei at 37 degrees C during 1 hour leads to a decrease of the amount of histone H1b and, to much more extent, H1a. In this case ATP, PP1 and NAD+ increase proteolysis of histone H1a but practically do not affect proteolysis of H1b. After 2-hours incubations histone H1a is completely digested but histone H1b is partially preserved: ATP in this case, as well as in spleen nuclei, decreases proteolysis of histone H1b. During the 3 hours incubation, when histones H H1a and H1b are completely digested, partial digestion of histone H3 being observed, ATP does not prevent from proteolysis of histone H1b. A protein appears between the H2A and H4 histones after heating at 37 degrees C in both spleen and liver rat nuclei. Neither ATP nor PP1 and NAD+ affect the amount of this protein. It is suggested that the location of histones H1a and H1b in different chromatin domains determines the digestion of these histones by ATP-dependent proteinases.
