CHANGES IN PATTERNS OF PROTEIN SYNTHESIS DURING MAMMALIAN CELL CYCLE

The pattern of protein synthesis during the G2 period of interphase in HeLa cells has been compared with the pattern of synthesis during an entire cell cycle in exponential growth. The patterns, as revealed by co-electrophoresis of the two populations of radioactive proteins on acrylamide gels, are very different. The differences are not due to selective or discontinuous degradation of proteins made radioactive during long or short exposures to tracer amino acids, nor do they arise from errors in the method of separation and counting. Similar differences are found between other phases of the cell cycle and the cycle as a whole, and between phases studied in pairs. Thus the reproductive cycle of eukaryotic cells not only involves translational shifts, an involvement already known to exist in consequence of studies in individual proteins, but it involves translational shifts of a magnitude sufficient for detection in bulk separation of the soluble proteins. © 1969.