PMID: 6172435Oct 1, 1981Paper

An autoradiographical study of amino acid and nucleoside incorporation during the cell cycle of Amoeba proteus

Journal of Cell Science
K I Mills, L G Bell

Abstract

The incorporation of tritiated thymidine, uridine and leucine, into the acid-precipitable material of DNA. RNA and proteins, respectively, was studied by autoradiography throughout the cell cycle of Amoeba proteus. DNA synthesis occupied the first 17 h of the cycle (57 h long) and 2 peaks between 0.5 and 9.13 h accounted for the majority of the thymidine incorporation. RNA synthesis was represented by a series of peak uridine grain counts, the 3 major peaks occurring at 10, 26-27 and 47-48 h. The incorporation of leucine also followed a pattern of peaks and dips, the main peaks occurring 1-2 h after the major increases in uridine incorporation. The fraction of label present over the nucleus decreased during the cell cycle, and this was probably due to a lowered incorporation of the leucine label by proteins synthesized in the cytoplasm and destined to become nuclear proteins. The incorporation patterns of 6 amino acids (arginine, aspartic acid, leucine, lysine, serine and valine) were studied individually during 3 periods of the cell cycle: 0-10 h (S phase); 20-30 h (early G2); and 40-50 h (mid-late G2). Variations in the intensity and timings of the incorporation maxima of the amino acids were observed, although the timings of...Continue Reading