Studies on nuclear deprimerones: isolation, fractionation, characterization and control of gene expression.

A procedure was developed for the isolation of low molecular weight peptides (deprimerones) from calf thymus nuclei and other tissues. These peptides are active in controlling transcription and translation in cell-free systems, and stabilize the double stranded structure of DNA. The procedure involves extraction of nuclei with 80% ethanol at pH 9.5 and fractionation of the extracted peptides on Sephadex G-25. The isolated deprimerones represent heterogenous peptidic fractions which can be separated into four activity peaks on Sephadex G-25 column and into ten peptidic spots on two-dimensional cellulose gel thin layer chromatography. One of the peaks is identical to a chromatin peptidic fraction isolated previously by binding to DNA-cellulose. The deprimerones contain about 8 or 9 different amino acids. It was demonstrated that the cytoplasm contains about 10% of the deprimerones present in nuclei. They are also ubiquitous, since they were found in each of the tissues studied: calf thymus, mouse thymus, mouse spleen and mouse liver.