Protein-Synthesizing Activity of Maize-Shoot Chromatin

Abstract

The evidence presented in this paper suggests that purified plant chromatin, similar to mammalian (SR Umansky et al., Eur J Biochem 1980 105: 117-129), has the ability to incorporate amino acids into acid precipitable material. The polypeptide-synthesizing system of chromatin seems to differ substantially from the classical polyribosomal translation mechanism in cytoplasm. When chromatin purified from 5-day-old etiolated maize (Zea mays) shoots was incubated with (14)C-labeled amino acids, label was incorporated into the trichloroacetic acid precipitable product. Chloramphenicol, pactamycin, and actinomycin D inhibited the incorporation almost completely, whereas treatment with cycloheximide, puromycin, or aurintricarboxylic acid did not affect the labeling. Preincubation with pancreatic RNase was also without effect, but treatment of chromatin with DNase I caused about 25% depression of label incorporation. A wheat germ translation system or its single components have no effect on the chromatin polypeptide-synthesizing activity beyond that expected for a simple addition. The protein-synthesizing system is tightly bound to chromatin and could not be removed by dissociation in 1 molar NaCl. The mean molecular weight of the major protein fraction synthesized in the presence of chromatin was 21 to 24 kilodaltons.