Post-transcriptional regulation of catalase synthesis in rat liver and hepatoma: Factors activating and inhibiting catalase synthesis

Abstract

Two factors acting on the post-transcriptional process for catalase synthesis were purified from the supernatant fractions of both hepatoma and normal liver tissue. One was an activating factor, F act . It passed through a DEAE -cellulose column equilibrated with Tris/K/Mg buffer + glycerol (50 mM-Tris-HCl, 5 m m-MgCl 2, 25 m m-KCl, 20% glycerol), but was retained on a DEAE-cellulose column equilibrated with Tris/glycerol buffer (10 m m-Tris·HCl, 20% glycerol) and was eluted with 0.2 m-KC1 in Tris/K/Mg buffer + glycerol. Its specific activity was increased 20-fold by the second Chromatographie treatment. Stimulation of catalase synthesis by polyribosomes and the supernatant fraction of hepatoma by purified F act was as great as that by the supernatant fraction of normal liver. The activity of this factor was lower in the supernatant of hepatoma than in that of normal liver. p]The other factor was an inhibiting factor, F inh . This factor remained in the pH 5-supernatant fraction and was retained on a DEAE-cellulose column equilibrated with Tris/K/Mg buffer + glycerol. Unlike most proteins in the pH 5 supernatant fraction, it was not eluted with 0.1 m-KC1 in Tris/K/Mg buffer + glycerol, but was subsequently eluted with 0.2 m-KC1 in the same buffer. The specific activity of inh was increased 3000-fold after rechromatography on a DEAE-cellulose column. The activity of this factor in hepatoma, in which catalase synthesis was greatly reduced, was much higher than that in normal liver. Examination of recoveries of these factors from a mixture of the supernatant fraction of hepatoma and normal liver revealed that the two factors did not inactivate each other in the soluble state, or irreversibly counteract the action of each other.